Components of the renin angiotensin system, namely renin, angiotensinogen, angiotensin I and II and aldosterone were measured in plasma of patients with hymenoptera venom anaphylaxis (n= 50) and healthy non-allergic controls (n= 25). Patients with a history of anaphylactic reactions to hymenoptera venom who did not undergo immunotherapy showed significantly reduced renin, angiotensinogen, angiotensin I and angiotensin II in plasma as compared with controls (P<0.05). There was no difference in the aldosterone concentration between patients and controls. Angiotensin I, angiotensin II, renin and angiotensinogen levels were the same in male and female patients. There was also no difference in the angiotensin I, II, renin or angiotensinogen levels between young and older patients. A significant inverse correlation between the severity of clinical symptoms and the plasma levels of renin (r=-0.382, P<0.001), angiotensinogen (r=-0.567, P<0.0001), angiotensin I (r= -0.656, P<0.0001) and angiotensin II (r = 0.0762, P < 0.0001) was found: the lower the levels the more severe the clinical symptoms. No correlation was found for aldosterone. Hymenoptera venom allergic patients with repeated anaphylactic reactions during hyposensitization did not tolerate the sting of a living insect (n= 6). In these patients, renin, angiotensinogen, angiotensin I and II remained significantly lower than in healthy non-allergic controls. Patients with successful immunotherapy (n= 27) who tolerated the sting of a living insect had renin, angiotensin I and II significantly higher than patients without immunotherapy. These findings suggest a possible role of the renin angiotensin system in hymenoptera venom anaphylaxis.