Toxic effects of 1,3,5-trinitrobenzene (TNB) in male and female rats were evaluated by feeding powdered certified laboratory chow diet supplemented with varied concentrations of TNB (0, 50, 200, 400, 800 and 1200mg kg-' diet) for 14 days. Food intake by female rats in 400, 800 and 1200mg TNB diet groups was reduced and resulted in a significant decrease in absolute body weights (BW). Food and water consumption by male rats in high-dose groups (800 and 1200 mg TNB kg-' diet) was also reduced and resulted in a significant decrease in body weight. The calculated average TNB intake (from 1200 mg TNB kg-' diet) was 92mg kg-' BW day-' for male rats and 80mg kg-' BW day-' for females. A decrease in testicular weight in males and an increase in spleen weight of both sexes in high-dose groups was noted. In addition, histopathological examinations revealed that the susceptible organs for TNB toxicity were kidney (hyaline droplets), spleen (extramedullary hematopoiesis), brain (hemorrhage, malacia and gliosis) and testes (seminiferous tubular degeneration). Hematology and clinical chemistry studies indicated a decrease in red blood cell count and hematocrit, a decrease in alkaline phosphatase, an increase in Heinz bodies and increased methemoglobin concentration as compared to controls in both sexes. A lowest observed adverse effect level of 4.41 mg TNB kg-' BW day-' was established based on the findings of this study.