The in vitro growth characteristics of melanocytes obtained from uninvolved and perilesional skin of vitiligo vulgaris subjects have been investigated in comparison to those from healthy adult donors. Normal human melanocytes have been found to grow exponentially in the presence of 10(-11) M cholera toxin and 10 ng/ml of 12-O-tetradecanoylphorbol-13-acetate in routine tissue culture media. They could be trypsinized up to 3-4 passages. Melanocytes of the uninvolved skin of vitiligo subjects manifested a lag of 8-11 days for the onset of growth and they could not be passaged. Melanocytes obtained from both hypo- and hyper-pigmented perilesional skin failed to grow under these conditions. Only in a few cases where the perilesional skin was normally pigmented did the melanocytes manifest some growth after a lag of 15 days. The initial seeding capacity of the melanocytes from uninvolved and perilesional skin of vitiligo patients were, respectively, 50% and 25% of the normal individuals. Vitiligo lesions themselves gave rise to unidentified dendritic cells that survived for 10-15 days without manifesting any growth. Our results suggest that melanocytes of individuals with vitiligo are defective. This fact has to be taken into account in any theory on the etiology of vitiligo.