The effect of Enalapril (angiotensin-converting enzyme inhibitor, ACE 1) on systolic blood pressure was studied on the Arabian camel (Camelus dromedarius). Ten camels were divided into two groups of five animals each. Group one animals were injected each with 0.2ug/100 kg Enalapril im, and those of group two were kept as untreated controls. Systolic blood pressure was measured before and at 2, 4, 8, 12 and 24 hours after treatment. Blood samples were concurrently collected with the blood pressure measurements for the determination of plasma concentration of sodium, potassium, plasma osmolality, renin activity (PRA), angiotensin II and arginine-vasopressin (AVP). Enalapril induced a sharp decrease in systolic blood pressure, lowered plasma [Na], plasma osmolality and angiotensin II. It also increased the concentration of [K], renin activity (PRA) and arginine-vasopressin (AVP) in the plasma. It is concluded that endogenous AVP and renin-angiotensin system plays an important role in maintaining blood pressure in camels.