A medical surveillance program has been established for 482 persons who were potentially exposed to polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and dibenzofurans from an electrical transformer fire in a Binghamton, NY office building in 1981. Blood samples were analyzed for serum concentrations of PCBs and for biochemical and hematologic parameters at the time of the fire and 9 to 12 mo later. Firefighters and individuals who were in the building for 25 hr or more were also asked about post-fire symptomatology and examined after 1 yr for disorders of the skin, eyes, liver, and neurologic system. The results indicated that reported exposure was positively related to mean serum PCB levels (p = .004). The means and individual values, however, were within the range reported by other studies of persons with no unusual exposures. Significant correlations were observed between serum PCB concentrations and levels of liver enzymes and lipids, but mean levels of these biochemical parameters were not associated with reported exposure after adjustment for relevant covariables. Approximately one-half of those examined had skin lesions, but no cases of chloracne were detected, and there was no clinical evidence of any other exposure-related systemic disorder. The data suggest that exposure to contaminants from the building did not result in substantial absorption or cause any major short-term health effects.