Effects of chrysene on immune functions were studied in female BALB/c mice. When mice were treated po with chrysene for 7 consecutive days, the antibody response was suppressed dose-dependently. Chrysene induced the enzyme activities of CYP LA and 2B time- and dose-dependently. In ex vivo lymphocyte proliferation, chrysene inhibited splenocyte proliferation by LPS and Con A. Moreover, the numbers of $CD4^+IL-2^+$ cells were reduced by chrysene. In conclusion, chrysene-induced immunotoxicity might be mediated, at least in part, via IL-2 production, and caused by mechanisms associated with metabolic activation.