Hepatitis B virus (HBV) genotypes and precore and core promoter mutations were determined in 318 patients with HBV. Patients infected with HBV genotype B had a higher median alanine aminotransferase level and bilirubin level and a lower median albumin level during exacerbations of disease, compared with patients infected with HBV genotype C (all P<.001). By logistic regression analysis, HBV genotype B infection (P=.014) and low albumin levels (P=.006) were independently associated with a higher risk of hepatic decompensation during severe exacerbations of disease. Patients infected with genotype B had a significantly higher mortality due to hepatic decompensation than did patients with genotype C (70% vs. 27.8%; P=.05).