The present study aimed at exploring the effect of antihistamine chloropheniramine maleate (H1-blocker) on liver and kidney functions as well as on blood count. 60 mature guinea pigs were used. Histamine or chloropheniramine maleate was given, either alone or together, intramuscularly for 7 successive days. At the end of the experimental period, blood samples were collected for determination of blood counts and of the levels of urea, creatinine, GOT, GPT, and alkaline phosphatase in the sera of different groups. The results showed significant groupwise variations in blood count, liver function as well as kidney function.