Non-steroidal anti-inflammatory drugs (NSAIDs) are in common use worldwide. These drugs may sometimes be used in high or toxic doses by mistake. In this study we investigated the effects of different doses of diclofenac sodium on liver and renal tissues. Forty albino adult male Wistar rats weighing 200 to 220 g were divided equally into four groups. The rats in the control group (n = 10) were each intramuscularly injected with 1 cc of physiologic saline. The other three groups were given diclofenac sodium doses. The rats in the first (n = 10), second (n = 10) and third (n = 10) groups were intramuscularly injected with diclofenac sodium at a low, medium and high dose of 50, 100 and 150 mg/kg live weight/day, respectively, every day for 5 days. At the end of the experimental period (5 days), after the animals were sacrificed, they were autopsied and liver and kidney tissue samples were prepared for histopathologic assessment.