A monoclonal antibody (Mab), designated 5B2, reacting with cell wall mannoproteins of Candida albicans has been purified and coupled to colloidal gold. The ability of the gold conjugated Mab to detect C. albicans antigens in serum during infection has been assessed in a dot immunobinding assay involving an immunogold silver enhancement procedure (GSS). A double blind study was made with sera from 140 guinea pigs, including 40 control animals and 100 infected intravenously with C. albicans. Sera from infected animals were collected either 2 days (4 animals), 15 days (9 animals), or 21 days (87 animals) after inoculation. The overall sensitivity, specificity and positive predictive value of the test were 89, 95, and 98%, respectively. However, differences were encountered in the ratio of positive tests in relation to duration of the infection. Mab-GSS dot immunobinding has also been applied, together with Mab co-counterimmunoelectrophoresis on successive sera from 2 patients who recovered from clinically and mycologically proven episodes of systemic candidosis. It was demonstrated that both patients synthesized antibodies against glycoproteins sharing the 5B2 epitope, which was initially present transiently in their sera.