Five females with nickel contact allergy and longstanding hand dermatitis were treated with oral methoxsalen and a series of whole-body UVA irradiations with a cumulative UVA dose of 30 to 58 J/cm2. Lymphocyte stimulation to nickel sulphate was determined prior to PUVA therapy, and monitored during the treatment and at 1 year after treatment. In 4 patients the cutaneous threshold to nickel sulphate patch testing was determined immediately post-PUVA and at 1 year. In all cases, the dermatosis cleared during the PUVA treatment. In 2 patients the immediate post-PUVA skin nickel reactivity was low compared with the 1-year follow-up value, while in 2 patients a progressive diminution of the skin reactivity was noticed. One patient was in clinical remission and had negative skin test at 1-year follow-up. In spite of diminished cutaneous sensitivity and/or clinical remission, the sensitivity of blood lymphocytes to nickel was approximately the same or increased, as determined by the lymphocyte transformation test. Thus no evidence was found to indicate that systemic, nickel-specific suppressive immune regulative mechanisms would have been activated by the treatment.