Precipitin antibodies to candida antigens were found by counterimmunoelectrophoresis (CIE) and double immunodiffusion (DID) in 100 per cent of sera from patients with significant candida infection. Such antibodies were also found by CIE in 63 per cent of individuals with candida colonization, 47 per cent of bacteremic patients, and 14 per cent of normal control subjects. No sera from these patients and normal control subjects were positive by DID. Serum precipitin titers by CIE in patients with significant candidiasis were significantly higher than in patients of the other groups. Detection of candida serum precipitins by CIE, when precipitin titers are obtained, compares favorably with DID as a diagnostic tool in significant candidiasis.