In healthy subjects and in subjects undergoing surgical intervention for neoplastic and other diseases, the behaviour of precipitating antibodies against soluble Candida albicans natigens was studied. In 13,7% of healthy controls the Ouchterlony test was positive. In subjects suffering from intestinal tract neoplasia, the percentage of positive tests was 26,6% before and 66,6% after the intervention. In other two groups of patients affected by neoplasia, the per cent positive results of the tests after intervention were, respectively, 50% and 63,1%. Among non neoplastic patients undergoing surgical treatment, after intervention 35% too proved positive. The data were confirmed by P.E.T. (partigen elution test): specific anti-Candida IgG, and in some cases IgA, could be demonstrated. The diagnostic value of positive Ouchterlony's test against superficial soluble Candida antigens after surgical intervention has been discussed.