Abstract To investigate the heterogeneity in antibody response to the various antigenic determinants of Candida albicans in patients with disseminated candidosis 201 serial serum samples from 45 patients with proven systemic candidosis were examined by immunoblotting (Western blotting) for antibodies to C albicans type A NCTC 3153. 40 patients had detectable antibody. 26 different antigen bands, ranging from 104 kD to 23 kD, were identified. Despite wide variation in the antigens recognised by different patients, the antibody responses fell into six patterns (A to F). 13 patients infected during an outbreak of systemic candidosis gave the same response (A). Of a further 7 patients with this response, 2 had isolates indistinguishable from the outbreak strain. Group B responses were associated with leukaemias and lymphomas. Groups C-F responses were seen in 9 patients. Production of antibody to a 47 kD antigen, common to all six groups, occurred in all those who recovered from the infection and may therefore be of prognostic significance. Whether this antigen could be used as the basis of a vaccine remains to be determined.