The occupational importance of tellurium and selenium is growing rapidly, but the biochemistry of exposure is poorly understood. Here we report the potential toxic effects of diphenyl diselenide (PhSe)(2), diphenyl ditelluride (PhTe)(2) and Ebselen in rats and mice. The results suggest that (PhTe)(2) is more toxic in rats than mice. (PhSe)(2), (PhTe)(2) and Ebselen are more toxic by intraperitoneal (i.p.) than subcutaneous (s.c.) route. Calculated LD50 for (PhTe)(2), i,p., was 0.65 mumol/kg in rats and 150 mumol/kg in mice, and LD50, s.c., was 0.9 mumol/kg in rats and > 500 mumol/kg in mice. Calculated LD50 for Ebselen, i.p., was 400 mumol/kg in rats and 340 mumol/kg in mice and LD50, s.c., was > 500 mumol/kg in both mice and rats. (PhTe)(2) at small doses increased 2-fold serum alanine aminotransferase. (ALT) and aspartate aminotransferase (AST) activities in rats. LD50 for all organochalcogens administrated in mice inhibited blood delta-ALA-D activity. The present study provides evidence for liver and renal toxicity of (PhTe)(2). (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.