Human antibody responses to human cytomegalovirus (HCMV) specific DNA-binding proteins were studied in serum samples by the Western blot technique. The molecular weights of six DNA-binding proteins found in HCMV-infected cells, ranged from 52kD to 18kD. The sera obtained from patients with acute HCMV infections reacted well with the six HCMV specific DNA-binding proteins. The strongest reactivity was observed with the 52kD and 35kD proteins. The sera from healthy HCMV seropositive donors reacted only with the 52kD DNA-binding protein as visualized in Western blots, but 2 out of 8 sera failed to react with any HCMV specific DNA-binding proteins.