Our previous studies in mice indicated that the exposure to vinyl chloride (VC) produced a state of immunostimulation. The metabolism of VC was an important factor in this phenomenon. The present paper describes the effects of VC exposure on induced immunologic responses in rabbits. No consistent effect of VC exposure was noticed on skin reactivity to tuberculin or serum anti-tetanus titers in sensitized rabbits. Vinyl chloride produced no change in the number of antibody secreting cells in the lymph nodes of immunized rabbits. An increase in the spontaneous splenic lymphocyte transformation in immunized rabbits was observed when the animals were exposed to VC. Two known metabolites of VC, namely thiodiglycolic acid and N-acetyl-S-(hydroxyethyl)-cysteine produced little or no effect when added to mouse splenic lymphocyte cultures in vitro but in vivo administration of thiodiglycolic acid produced apparent immune stimulation in mice. The study indicated that although VC may cause an apparent enhancement of immune reactivity, it does not alter the immunologic response to simultaneously administered antigens.