Polymorphisms in the IL28B (interleukin-28B) gene region are important in predicting outcome following therapy for chronic hepatitis C virus (HCV) infection. We evaluated the role of IL28B in spontaneous and treatment-induced clearance following recent HCV infection. The Australian Trial in Acute Hepatitis C (ATAHC) was a study of the natural history and treatment of recent HCV, as defined by positive anti-HCV antibody, preceded by either acute clinical HCV infection within the prior 12 months or seroconversion within the prior 24 months. Factors associated with spontaneous and treatment-induced HCV clearance, including variations in IL28B, were assessed. Among 163 participants, 132 were untreated (n = 52) or had persistent infection (infection duration >/=26 weeks) at treatment initiation (n = 80). Spontaneous clearance was observed in 23% (30 of 132 participants). In Cox proportional hazards analysis (without IL28B), HCV seroconversion illness with jaundice was the only factor predicting spontaneous clearance (adjusted hazards ratio = 2.86; 95% confidence interval = 1.24, 6.59; P = 0.014). Among participants with IL28B genotyping (n = 102 of 163 overall and 79 of 132 for the spontaneous clearance population), rs8099917 TT homozygosity (versus GT/GG) was the only factor independently predicting time to spontaneous clearance (adjusted hazard ratio = 3.78; 95% confidence interval = 1.04, 13.76; P = 0.044). Participants with seroconversion illness with jaundice were more frequently rs8099917 TT homozygotes than other (GG/GT) genotypes (32% versus 5%, P = 0.047). Among participants adherent to treatment and who had IL28B genotyping (n = 54), sustained virologic response was similar among TT homozygotes (18 of 29 participants, 62%) and those with GG/GT genotype (16 of 25, 64%, P = 0.884). Conclusion: During recent HCV infection, genetic variations in IL28B region were associated with spontaneous but not treatment-induced clearance. Early therapeutic intervention could be recommended for individuals with unfavorable IL28B genotypes.