Thirty-one Japanese nonresponders to subcutaneous hepatitis B vaccination and 15 medical personnel who were accidentally exposed to specimens positive for hepatitis B e antigen and were given hepatitis B immunoglobulin were intradermally immunized with 5 micrograms of plasma-derived hepatitis B vaccine every 2 weeks until delayed type hypersensitivity skin reaction to hepatitis B surface antigen became positive. Thirty (97%) of the 31 nonresponders developed delayed type hypersensitivity skin reactions to hepatitis B surface antigen after 2.3 +/- 1.2 (mean +/- SD) revaccinations. Twenty-nine (94%) of the 31 nonresponders had anti-hepatitis B surface antigen antibody levels greater than 10 IU/L. The immunoglobulin subclass of the antibody to hepatitis B surface antigen was mainly IgG1. After 1 year, 23 (74%) of the 31 nonresponders continued to have anti-hepatitis B surface antigen antibody levels greater than 10 IU/L. Persons accidentally exposed to specimens positive for hepatitis B e antigen developed delayed type hypersensitivity skin reactions to hepatitis B surface antigen following 3.1 +/- 1.1 revaccinations. None developed clinical hepatitis. There was no production of anti-hepatitis B core antigen antibody 1 year after exposure, indicating that protection was 100%. Intradermal hepatitis B vaccination is useful in reversing nonresponsiveness to hepatitis B surface antigen and for prophylaxis after exposure.