Of the 697,000 U.S. troops who served during Operation Desert Shield and Desert Storm, more than 100,000 have registered with the Department of Veterans Affairs (VA) or the Department of Defense (DOD), saying they have health concerns. While most of these veterans have been diagnosed with a variety of conditions, more than 15,000, or about 20 percent of those examined, have undiagnosed symptoms, which commonly include fatigue, muscle and joint pains, headaches, memory loss, skin rash, diarrhea and sleep disturbances.

When asked to describe their health, 26 percent of those who registered with the VA said "poor;" 42 percent, "all right;" and the remaining 32 percent, "good."

Yes. Any Persian Gulf veteran who is concerned about his or her health is encouraged to take advantage of the free, confidential registry program. Veterans who are still on active duty can register with DOD by calling 1-800-796-9699. Those who have left active military service should call the VA at 1-800-PGW-VETS.

In fact, 12 percent of veterans who have already completed a VA examination did not report having health problems but were concerned that they might develop them in the future.

This is a very difficult question to answer because cancer and other common ailments, which account for 70 percent of all illness reported by Persian Gulf veterans, may occur with increased frequency in individuals following exposure to a variety of toxic substances. Cancer, however, may require 20 to 30 years to develop following a toxic exposure.

Early indications are that Persian Gulf veterans have not experienced an increase in hospitalizations or death from disease or illness when compared to their military peers who did not serve in the Gulf War. However, more research and time are required to determine if the delayed occurrence of commonly diagnosed conditions is increased in Persian Gulf veterans.

"Gulf War Syndrome" is a non-scientific label that has frequently been used to describe those veterans with unexplained illnesses often characterized by fatigue, joint pain, skin rash, memory loss and/or diarrhea. Five panels of experts agree that this group of veterans is probably not suffering from a single, common ailment, but rather from a variety of illnesses with overlapping symptoms.

A number of potential causes have been postulated and investigated, but to date no single theory appears likely to explain all of these undiagnosed conditions. Among some of the more common theories are: exposure to low levels of chemical agents; an unusual chronic infectious disease; exposure to biologic warfare agents; side effects of vaccines or medications administered to Gulf War participants; or some combination of these factors.

In tens of thousands of protocol medical examinations of Persian Gulf veterans to date, neither VA nor DoD medical authorities have found evidence of infectious diseases beyond the range of illnesses common in the population at large. Research studies now in progress will provide more scientific answers to this question, but no rigorous, reproducible research to date has established that Gulf War veterans' illnesses are caused by an infectious agent.

VA is concerned about media reports on hypotheses that previously unidentified organisms could be responsible for disease transmission. Absent credible scientific evidence, this grave disservice to Persian Gulf veterans and their families could cause unwarranted discrimination in the workplace, schools or community. When plausible hypotheses are put forward, federal investigators examine them and encourage careful private research as well.

Post-traumatic stress disorder (PTSD) is an anxiety disorder commonly diagnosed in individuals exposed to extraordinary stress or trauma, such as that associated with military combat. Symptoms include agitation, disturbed sleep and mood swings. PTSD has been diagnosed in a number of Gulf War veterans, but this disorder accounts for less than 5 percent of all illnesses diagnosed in Gulf War veterans participating in the VA registry.

This is a very real possibility that is being actively investigated. Stress can cause psychological as well as physical effects. New research shows that stress can affect the nervous system, immune system, and hormones in the body. Clearly, chronic stress has been associated with a variety of common ailments, such as ulcers, high blood pressure and certain types of heart disease. However, research is needed to determine if stress caused physical illness in Persian Gulf veterans. Stress would not account for all illnesses reported by Persian Gulf veterans.

DoD information suggests that a number of U.S. troops may have been exposed to low levels of a class of chemical warfare agents known as nerve agents. These compounds alter nerve transmissions and result in a variety of symptoms, including a runny nose and tearing; changes in vision; increased salivation; difficulty in breathing; stomach cramps; muscle twitching; and convulsions and death at higher exposure levels. These symptoms develop within minutes of exposure to nerve agents.

Individuals who survive a serious acute poisoning may experience delayed effects on the nervous system and, in some cases, have shown very subtle changes in the brain waves or EEG. However, these long-term effects have not been confirmed to date in individuals exposed to very low levels of nerve agents.

Comprehensive medical care is available at no cost to the veteran through the VA for Persian Gulf veterans with medical problems thought to be possibly related to a hazardous exposure during their service in the Gulf War. Care may not be available, however, or may require co-payment by the veteran, if the illness is determined to be clearly unrelated to their Persian Gulf service.

If an illness or injury associated with service in the Persian Gulf results in a persistent disability, the veteran may be eligible for disability compensation from the VA. New legislation also authorizes disability compensation for Persian Gulf veterans with chronic, undiagnosed illnesses resulting in a permanent disability that developed after they left the Persian Gulf. VA published regulations April 29, 1997, to expand eligibility for compensation for Persian Gulf War veterans with undiagnosed illnesses to replace a previous two-year limitation, extending through Dec. 31, 2001, the period in which Gulf War veterans' undiagnosed illnesses may become manifest in order to be presumed related to their service.

Several prestigious government and non-government scientific panels have reviewed Gulf War illnesses and possible factors that may have led to the occurrence of a variety of illnesses, but have concluded that the illnesses are likely the result of many different causes with overlapping symptoms. These panels include three Institute of Medicine committees, the Defense Science Board, a National Institutes of Health workshop, the VA Persian Gulf Expert Scientific Committee, and the Presidential Advisory Committee on Gulf War Veterans' Illnesses.

A number of recommendations from the panels have proved extremely helpful in planning research to more fully understand both the nature and causes of these illnesses. None of the findings to date fully explains the cause or causes of Persian Gulf illnesses.

A large number of studies are now in progress that will contribute to our understanding of Gulf War illnesses, including epidemiologic studies that will compare the types and frequency of illnesses in Gulf War veterans compared to veterans who did not serve in the Gulf War. This work will provide valuable information about what types of illness may have resulted from military service in the Gulf War.

Preliminary results from several of these studies should be available within the next year. In addition, more than 90 research studies are under way that will examine possible health consequences of exposure to a variety of factors present in the Persian Gulf, such as depleted uranium, pesticides, pyridostigmine bromide and chemical warfare agents.