Skin tests with autologous cholesteryl hemisuccinate-treated tumor cells were performed in Stage II malignant melanoma patients. In the majority of cases an evident reaction having features of delayed type hypersensitivity was noted. No significant correlation between this reactivity and subsequent course of the disease was found. The same was true for the results of DNCB and PPD skin testing. An analysis of the results of all three tests in the same patient revealed no prognostic significance of this score either.