Biomarkers of exposure were applied to a cohort of U.S. Army soldiers who were deployed to Kuwait and Saudi Arabia in 1991 in the aftermath of the Persian Gulf War. The U.S. Army Environmental Hygiene Agency (currently the U.S Army Center for Health Promotion and Preventive Medicine) monitored air and soil for ambient PAHs. In addition, a group of 61 soldiers kept diaries of daily activities. These soldiers provided blood and urine samples in June in Germany before deployment to Kuwait, in August after 8 weeks in Kuwait, and in October, one month after the return to Germany. DNA, prepared from white blood cells, was assayed for PAH-DNA adducts by immunoassay and bulky aromatic adducts by P-32-postlabeling, Urinary 1-hydroxypyrene-glucuronide (1-OH-PG) was determined by synchronous fluorescence spectrometry. Contrary to expectations, environmental monitoring showed low ambient PAH levels in the areas where these soldiers were working in Kuwait. In addition, literature values for ambient PAH monitoring in Germany in 1990 suggest that the soldiers may have been exposed to higher levels of ambient PAHs in Germany than in Kuwait. Blood cell DNA adduct levels were lowest in Kuwait and increased significantly after the return to Germany. Also, urinary 1-OH-PG levels were lowest in Kuwait and highest in Germany. This study demonstrates modulations in PAH exposure biomarker levels that appear to correlate with ambient PAH exposure.