A passive haemagglutination (PHA) assay for the detection of varicella-zoster virus (VZV) antibody was prepared with purified viral glycoproteins. Serum samples from vaccinees with live attenuated varicella vaccine, and of zoster patients, were measured for antibody titres against VZV with PHA, complement fixation (CF) and immune adherence haemagglutination (IAHA) assays, and the results compared. Antibody development could be detected as early as 3 weeks after vaccination, by both PHA and IAHA tests, but not with the CF test. Significant rises in VZV antibody in zoster patients were detected by both PHA and CF tests several days after onset. No cross-reaction was observed using HSV PHA among the vaccinees and the zoster patients. The VZV PHA assay could be used as a monitor of vaccination and a tool for differential diagnosis.