Narrow band UVB is succeeding psoralen and UVA irradiation as the main treatment of vitiligo vulgaris in several European countries. Vitamin B12 and folic acid deficiency in some vitiligo patients has prompted researchers to investigate the efficacy of these vitamins in the treatment of vitiligo. In the present controlled study we investigated the value of narrow band UVB phototherapy in the treatment of vitiligo and the possible additive effect of vitamin B12 and folic acid. Twenty-seven patients with long-term stable vitiligo were included and randomized in a "UVB only" (UVB) or "UVB combined with vitamin B12 and folic acid" (UVB+) group. Patients were irradiated thrice weekly for one year, whilst repigmentation was carefully monitored. In 92% (25/27) of the patients up to 100% repigmentation was seen. Repigmentation was notable in lesions on the face, neck and throat, lower arm, chest, back and lower legs, whilst repigmentation on the hands, wrists, feet and ankles proved to be minimal. Maximum repigmentation rates did not differ significantly between the UVB group and the UVB+ group. Our study reconfirms that narrow band UVB phototherapy is an effective treatment for vitiligo and shows that co-treatment with vitamin B12 and folic acid does not improve the outcome of treatment of vitiligo with narrow band UVB phototherapy.