The evaluation of efforts to prevent hepatitis B virus (HBV) infection in the United States requires accurate measures of hepatitis B vaccination coverage among children and adults at risk for infection. Although vaccination coverage among children is obtained by nationwide surveys, vaccination coverage among adults at risk for HBV infection has not been well characterized. To estimate hepatitis B vaccination coverage among young men who have sex with men (MSM) (a group known to be at high risk for HBV infection and for whom hepatitis B vaccine has been recommended since 1982), CDC analyzed serologic data from the 1992-1993 Young Men's Survey (YMS) conducted by the San Francisco Department of Public Health. This report summarizes the results of that analysis, which indicate low hepatitis B vaccination coverage among young MSM in the San Francisco Bay area.