Injection drug use is the leading risk factor for infection with hepatitis C virus, and interferon (IFN) treatment in this context is associated with a poor rate of adherence. In this article, we review our experience with injection drug users with acute hepatitis C who are treated with pegylated IFN- alpha -2b for 12 weeks. Acute hepatitis C was diagnosed according to standardized criteria, and patients were treated with a median dosage of IFN- alpha -2b of 1.33 microg/kg per week. A sustained virological response was achieved in 17 (74%) of 23 patients. A sustained virological response was achieved in 14 (87%) of 16 patients treated with a dosage of >or=1.33 microg/kg per week and in 3 (43%) of 7 patients treated with a lower dosage. Sustained virological response was significantly associated only with a pegylated IFN- alpha -2b dosage >or=1.33 microg/kg per week (P=.022). A 12-week regimen of pegylated IFN to treat injection drug users with hepatitis C has a compliance that is much higher than that reported with a 24-week regimen. Adverse effects are minimal if patients are carefully selected.