BACKGROUND This study investigates anecdotal reports that have suggested adverse health effects associated with acute or chronic exposure to jet fuel. METHODS JP-8 exposure during the course of the study day was estimated using breath analysis. Health effects associated with exposure were measured using a neurocognitive testing battery and liver and kidney function tests. RESULTS Breath analysis provided an estimate of an individual's recent JP-8 exposure that had occurred via inhalation and dermal routes. All individuals studied on base exhaled aromatic and aliphatic hydrocarbons that are found in JP-8. The subject who showed evidence of the most exposure to JP-8 had a breath concentration of 11.5 mg x m(-3) for total JP-8. This breath concentration suggested that exposure to JP-8 at an Air Guard Base is much less than exposure observed at other Air Force Bases. This reduction in exposure to JP-8 is attributed to the safety practices and standard operating procedures carried out by base personnel. The base personnel who exhibited the highest exposures to JP-8 were fuel cell workers, fuel specialists and smokers, who smoked downwind from the flightline. CONCLUSIONS Although study-day exposures appear to be much less than current guidelines, chronic exposure at these low levels appeared to affect neurocognitive functioning. JP-8-exposed individuals performed significantly poorer than a sample of non-exposed age- and education-matched individuals on 20 of 47 measures of information processing and other cognitive functions.