Pigmentation in a Causasian male, resulting from bleomycin therapy for Hodgkin's disease, has been studied ultrastructurally. The melanocytes, though present in normal numbers, showed several abnormalities; the endoplasmic reticulum and the Golgi apparatus were were well developed and the mitochondria were enlarged. Lipid inclusions in the endoplasmic reticulum and numerous autophagocytic vacuoles, some containing lipids were observed. Transfer of melanosomes to keratinocytes appeared to be increased. The melanosomes, which measured less than 0.55 mu were dispersed in the cytoplasm and did not form complexes, as has been observed with nitrogen mustard. The increase of melanocytic activity and the disturbance of melanosome transfer are discussed.