Attempts were made to isolate an antigen(s) from Candida albicans suitable for detecting hypersensitivity in a murine model of candidiasis. Using footpad reactivity in cutaneously infected animals as the assay, comparisons were made of two commercial extracts and cell wall and cytoplasmic preparations made in the laboratory. An extract of the cell wall, a glycoprotein (GP) removed with ethylenediamine, and an extract prepared from the membrane fraction of disrupted C. albicans blastospores proved most useful in demonstrating delayed hypersensitivity in the murine model. The activity of the GP fraction was considerably reduced by oxidation with periodate and was abrogated entirely by digestion with proteolytic enzymes. The extract from the membrane fraction was obtained by incubating the insoluble membrane fraction with phosphate-buffered saline, pH 7.4, at 50 degrees C, and the proteins in the extract were subsequently precipitated with ammonium sulfate to yield a test preparation that was approximately 75% protein and 25% carbohydrate. The precipitated extract was designated ppt-HEX. Footpad reactivity to ppt-HEX could be transferred with cells and not with serum if the cells were taken from animals at the appropriate time after sensitization. Since the membrane and GP fractions appear to elicit true delayed hypersensitivity reactions, further investigations into their specificity and biochemistry seem warranted.