Previous reports documented the fact that some patients with mucocutaneous candidiasis and vitiligo have a complement-fixing anti-pigment-cell factor in their serum. We examined sera from seven patients with mucocutaneous candidiasis without vitiligo. Three of the seven sera contained the anti-pigment-cell factor. We suggest that these anti-pigment-cell factors, which are most probably antibodies, are not cytotoxic for pigment cells and, thus, not the cause of vitiligo. The association of vitiligo and anti-pigment-cell factors with the syndrome of mucocutaneous candidiasis implicates the immune system are a causal factor of vitiligo.