Experimental uveitis was successfully induced in rabbits by bovine serum albumin (BSA). Tetrandrine (Tet), 50 mg/kg/d i.p., and dexamethasone (Dex), 5 mg/kg/d i.p., for 8 d showed marked inhibition of uveitis in rabbits. Eight d after drug administration, ocular inflammation was markedly inhibited. The maximum inhibitory rate of Tet and Dex was 48.9% and 56.0%, respectively. The protein content of the aqueous humor (PAH) was reduced significantly; phytohemagglutinin (PHA)-induced peripheral T lymphocyte transformation of 3H-thymidine (3H TdR) incorporation was suppressed markedly; and serum circulating immune complexes (CIC) also were reduced. Four d after Dex withdrawal, ocular inflammation, PHA and CIC rose again, but these parameters were not changed after Tet withdrawal. These results suggest that Tet is an effective inhibitory agent on BSA-induced uveitis in rabbits. The inhibiting action may be related to the suppression of cellular and humoral immune function and, unlike Dex, Tet did not produce withdrawal rebound.