Alkaline phosphatase (ALP) is an enzyme in the cells lining the biliary ducts of the liver. This study aimed to evaluate whether serum alkaline phosphatase level is disturbed in the liver of heroin addicts or not. Data was collected from the patients who were admitted in the addiction center of Punjab institute of Mental Health. Alkaline phosphatase level, HCV and HBV were checked in heroin addicts and control subjects. Study was conducted on total 25 heroin addicts. Nearly 36% heroin addicts showed elevated level of alkaline phosphatase as compared to normal level of this enzyme. Only 4% addicts showed value below normal.