We hypothesized that acute infection with human immunodeficiency virus (HIV) would diminish immunoregulation of chronic hepatitis B (CHB), resulting in higher blood hepatitis B virus (HBV) DNA levels. To test this hypothesis, we evaluated sequential HBV DNA levels in stored serum samples obtained from 9 men with CHB who acquired HIV infection. Three patterns of changes in HBV DNA levels were noted after HIV seroconversion. One man experienced the expected increase in HBV DNA, 3 men had stable HBV DNA levels, and, unexpectedly, 5 men had a mean decrease of 6.29 log10 copies/mL in the HBV DNA level, with hepatitis B e antigen no longer detectable in 4. Acute HIV infection is not consistently associated with an increased blood HBV DNA level. Additional research is needed to understand the mechanism for the unexpected reductions in HBV DNA levels associated with acute HIV infection.