To determine whether or not bisphenol A affects the Immune system, female ICR mice were treated bisphenol A (BPA) orally at the doses of 100, 500 and 1,000 mg/kg for 30 consecutive days. Four days before enumerating Plaque -forming cells (PFCs) mice were immunized intraperitoneally with sheep red blood cells (SRBCs). The spleen cellularity and PFC/spleen were significantly reduced by 30-day exposure to BPA (1,000 mg/kg/day), but the PFC/10$^$6/ spleen cells was slightly decreased.. When splenocytes isolated from the mice exposed to BPA for 30 days were cultured in the presence of LPS, Con A or PHA with IL-2, the lymphocyte proliferation ex vivo was not significantly suppressed by BPA. Our present results indicated that 30-day exposure of mice to BPA might have mild immunotoxic potential.