Spirometric findings (forced vital capacity [FVC], forced expiratory volume at one second [FEV1], FEV1/FVC) in a population of capacitor workers with occupational exposure to polychlorinated biphenyls (PCBs) are described during active PCB use (1976) and following the PCB ban (1979 and 1983). The initial finding of restrictive impairment (16%) in 1976 was not supported by chest roentgenogram findings, nor confirmed in 1979 and 1983, and was interpreted as artifactual due to test operator inexperience and inadequate expiratory efforts. Obstructive impairment was consistently found in 15% of the total population in 1976 and 1979. A history of respiratory illness and/or symptomatology and reduced FEV1/FVC was correlated with PCB exposure and serum PCB levels (lower homologs) in females in 1976, but not in males. Smoking was correlated with reduced FEV1values. No correlation of spirometric variables with past exposure or serum PCB levels was found for either sex in 1979.