Daily exposure to heat stress causes sustained elevation of blood pressure in rats. It is known that the renin-angiotensin system is activated during episodes of behavioral stress, and the purpose of this work was to assess the action of captopril in the development of stress induced hypertension in rats. Animals were divided into four groups. The first group served as a control, while the other groups were subjected to heat stress of 40C and high hamidity of 80% for 10 successive days. The second group was served as heat stress, while the third and the fourth groups were received low and high doses of captopril (0.7 & 1.4 mg/kg. b.wt., respectively). After 10 days of treatment, half of animals from each group were decapitated and brain, liver, muscle, heart and kidney were separated and analysed. The other half of animals were left for another 10 days without any additional treatment for recovery.The results revealed a significant decrease in total protein of liver, heart, kidney, total lipids of heart, muscle and brain and total cholesterol of liver. On the other hand, insignificant change was noticed in muscle and brain total protein. Similarly, AST and ALT activities were also within the normal values for all the organs examined.Results exhibited that renin-angiotensin system may be important in the development of stress-induced hypertension in rats.