The preventive effect of zinc compounds on bone loss in streptozotocin (STZ)-diabetic rats was investigated. Rats received a single subcutaneous administration of STZ (6.0 mg/100 g body weight), and 7, 14 or 21 days later the animals were sacrificed by bleeding. STZ administration caused a significant decrease in body weight and a significant increase in serum glucose and triglyceride levels, indicating diabetic condition. Femoral-diaphyseal and -metaphyseal alkaline phosphatase activity, calcium and deoxyribonucleic acid (DNA) contents were significantly decreased by STZ administration, showing that diabetic condition causes bone loss. Zinc sulfate (2.5 mg Zn/100 g) or zinc acexamate (2.5 mg Zn/100 g) was orally administered once daily for 14 days to rats received a single subcutaneous administration of STZ (6.0 mg/100 g). STZ administration-induced increase in serum glucose and triglyceride levels and decrease in body weight, femoral-diaphyseal and -metaphyseal alkaline phosphatase activity, DNA and calcium contents were significantly prevented by the administration of zinc acexamate. The preventive effect of zinc sulfate on bone components was not seen. The present results demonstrate that the administration of zinc acexamate has a preventive effect on bone loss in STZ-diabetic rats in vivo.