This study aimed to evaluate the efficacy and safety of a 6-month course of ribavirin (Rb) (1200 mg/day) in the treatment of chronic hepatitis B (CHB). Sixty patients with CHB were randomly assigned in a double-blind placebo (Pl) controlled study; 30 patients received oral Rb (1200 mg/day) and 30 received Pl for 24 weeks. Patients were hepatitis B surface antigen (HBsAg); hepatitis B envelope antigen (HBeAg); and hepatitis B virus (HBV)-DNA-positive, with alanine aminotransferase (ALT) levels 1.5 times higher than normal values. Clinical evaluations and laboratory tests were carried out at regular intervals; tests included total blood cell count, liver function tests, and HBV serum markers. Baseline and control liver biopsies were carried out. HBeAg seroconversion occurred in 50.0% of the patients in the Rb group (vs 6.6% in the Pl group; P = 0.00019); HBV DNA negativization occurred in 33.3% in the Rb group (vs 6.6% in the Pl group; P = 0.009); and improvement in the necroinflammatory index occurred in 53.3% in the Rb group (vs 23.3% in the Pl group; P = 0.02). The drug was well tolerated; the most important side effect in the Rb group was hemoglobin reduction, which was reversible once the treatment was stopped. Ribavirin was an effective treatment, demonstrated by decreased ALT levels, alleviation of histological damage, seroconversion of HBeAg, and HBV-DNA negativization; Rb may be an alternative agent in the treatment of CHB, without significant side effects.