We studied, in vivo, the effects of a calcitriol-containing ointment (3 micrograms of calcitriol per gram of petrolatum) topically applied on skin lesions in children affected by psoriasis vulgaris. Each patient was instructed to apply the ointment, about 1 g once a day at bedtime followed by occlusive dressing with plastic wrap, on one-side lesion (treated) and petrolatum alone on the equivalent controlateral site (placebo) (total weekly dose of calcitriol: approximately 21 micrograms/patient). After 4 weeks of topical treatment all children showed a complete clearing of their skin lesions on the treated side, without appreciable changes on the placebo side. Serum ionised calcium, calcium and calcitriol levels or urinary calcium excretion did not vary significantly throughout the period of therapy. These findings suggest that topical calcitriol may be an effective and safe alternative therapy for psoriasis in children.