This paper provides evidence that melanocytes are still present in the depigmented epidermis of patients with vitiligo even after stable disease of 25 years' duration. Melanocyte cultures were successfully established from depigmented epidermal suction blister tissue of all 12 randomly selected patients and these cells produced melanin. Even under in vitro conditions, vacuolation of melanocytes was demonstrated in five patients with active disease, which was reversible upon exogenous addition of bovine catalase to the culture medium. Full skin biopsies from 17 patients with vitiligo, obtained from depigmented and normally pigmented areas, confirmed the involvement of melanocytes, keratinocytes, and Langerhans cells in this disorder. In addition, the presence of clustered and single pre-melanosomes in basal and supra-basal keratinocytes of lesional and normal epidermis, as well as the retention of single melanocytes in lesional epidermis, was demonstrated by light and electron microscopy. Upon topical application of a narrow band UVB-activated pseudocatalase, vacuolation, granulation, and dilatation of the endoplasmic reticulum completely recovered, but the ectopic pre-melanosome shedding remained. Taken together, these observations indicate that melanocytes are never completely absent in the depigmented epidermis and that these melanocytes can recover their functionality in vivo and in vitro upon the removal of hydrogen peroxide. Furthermore, this study supports the concept that vitiligo involves the entire epidermal unit in both depigmented and 'normal' pigmented skin.