A patient with chronic mucocutaneous candidiasis resistant to all tropical therapy has had extensive tests of immunological function carried out before and after administration of transfer factor. Immunological testing has been both specific, directed at responses to candida antigen, and non-specific, directed at general assessment of the patient's immune status. Transfer factor has been administered on three occasions in the past year. After each treatment temporary clinical improvement accompanied by changes in both specific and non-specific immunological responses have been observed. The possible mode of action of transfer factor in this case is discussed.