Hazardous materials releases can cause substantial morbidity and mortality, and an increasing number of communities have developed hazardous materials (HAZMAT) teams to deal with such incidents. Little is known, however, about the health effects of chemical accidents on HAZMAT team participants. Baseline and periodic medical surveillance of all 40 fire fighters from the Metrofire Haz-mat team was conducted in 1992/1993 and 1995, respectively. A database on incidents responded to by the team during the study period was also developed. From June 1990 through April 1995, the team responded to a total of 34 hazardous materials incidents. No injuries to HAZMAT team members were reported. Few biochemical abnormalities were observed, and those that were could not be linked to specific exposures or incidents. Four individuals had abnormal audiometry on both occasions. There was a trend toward a lower percent predicted FEV1for the entire group on follow-up: 106 ± 13% vs 105 ± 12%, P = 0.07. For fire fighters older than age 35 (n =21), the percent predicted FEV1was significantly lower at follow-up: 108 ± 12% vs 106 ± 14%,P =0.01. The results suggest significant noise exposure and exposure to pulmonary irritants, which support the use of baseline and periodic audiometry and spirometry. The potential utility of other laboratory testing is also discussed.