The role of non-injecting drug abuse in viral hepatitis has not been studied widely and is not well understood. A total of 301 substance abusers, residents of a detoxification/rehabilitation unit, were investigated for exposure to hepatitis B virus (HBV) and hepatitis C virus (HCV). Samples of serum were tested for anti-HCV and anti-HBc antibodies and HBsAg. All of the patients were non-injecting drug users (non-IDUs). The prevalence of anti-HCV was 1.7%; anti-HBc was found in 28.7% and HbsAg in 0.6% of patients. Anti-HCV positivity correlated with the presence of elevated aminotransferases (80%). Exposure to HBV correlated significantly with gender (p < 0.05); age (p < 0.05); and duration of substance abuse (p < 0.05). No significant correlations were found between HCV and/or HBV infection, the drug of abuse, HIV, HTLV-1 or syphilitic infection. Residential detoxification/rehabilitation provides an opportune moment to identify and treat HCV positive substance abusers in the attempt to avert the severe hepatic sequelae. Measures which exclude substance abusers from volunteer blood donation should be considered.