Effects of selected polychlorinated biphenyls (PCBs) on vesicular catecholamine release from rat PC12 phaeochromocytoma cells have been measured using carbon fiber microelectrode amperometry. Exocytotic responses were evoked by superfusion of single PC12 cells with high K(+) saline. Subsequent exposure of the same cells to saline containing the nonplanar congener 2,2'-dichlorobiphenyl (PCB 4) and the coplanar congener 3,3',4,4',5-pentachlorobiphenyl (PCB 126) at concentrations between 5 and 25 microM for 15 min caused an enhancement of the frequency of basal vesicular catecholamine release at the lower concentrations but not at the high concentrations tested. The nonplanar congener 2,2',3,3',4,4'-hexachlorobiphenyl (PCB 128) did not affect basal release. The PCBs caused only marginal effects on the frequency of evoked events during high K(+) stimulation and did not affect vesicle contents. Prolonged exposure of PC12 cells to low concentrations of the same PCBs in the culture medium for a period of 3 days did not cause significant changes in vesicle contents. The results demonstrate that low concentrations of PCBs may cause acute vesicular catecholamine release but do not influence the contents of catecholamine-containing vesicles either on acute or after subchronic exposure.