Stage 1 of this Phase I/II study to evaluate the safety and efficacy of lobucavir in the treatment of patients with chronic hepatitis B was completed on 5/7/97. Twenty-two subjects were enrolled in the study, 3 from UAB. Lobucavir at doses of 200 mg bid and 200 mg qid was associated with 2-4 log reductions in serum HBV DNA levels during the 28 days of dosing, whereas there was no significant reduction in patients treated with placebo. However, within 4 weeks of completing the dosing, the HBV DNA levels returned to baseline in all but one lobucavir recipient. That patient subsequently seroconverted during the post-dosing phase. Adverse events were infrequent, and no difference was seen among the two lobucavir groups and the placebo group.