Anti-tumour antibody was sought in the sera of three groups of patients; idiopathic vitiligo, malignant melanoma and miscellaneous skin disorders. No precipitating antibody to a series of prepared pigmented tumour antigens was demonstrated. All sera were tested for a number of auto-antibodies. No significant differences were detected between the groups. The evidence for an immunological factor in the causation of vitiligo remains circumstantial only.