The epidemiological features of acute symptomatic viral hepatitis were examined in 151 consecutive, hospitalized drug abusers. Hepatitis B was diagnosed in 101 patients (66.8%), hepatitis A in 13 (8.6%) and non-A, non-B hepatitis in 35 (23.1%). Non-A, non-B hepatitis was significantly more prevalent among drug abusers than in an age-matched control population of non-drug abusers. Moreover, the mean duration of parenteral drug abuse was significantly lower among non-A, non-B cases than in patients with hepatitis A or B. These results suggest a wide circulation of both hepatitis B virus and non-A, non-B agent(s) among drug abusers in our area. These patients most likely represent a main reservoir of non-A, non-B infection due to the high rate of chronicity reported for non-A, non-B hepatitis.