Although potent, topical corticosteroids offer effective and rapid healing of psoriatic lesions. Their long term use is limited because of the risk of side effects. Calcipotriol is safe for long-term treatment, but its initial efficacy is lower than with topical corticosteroids.To investigate whether 2 weeks of treatment with clobetasol propionate 0.05% ointment bd followed by 4 weeks of treatment with calcipotriol 50 microg/g bd would offer therapeutic advantages over 6 weeks of continuous treatment with calcipotriol.Forty-nine patients with moderate to severe plaque psoriasis were recruited from five centres in Norway. In a randomised, double-blind, right- versus left-side comparison, ointments were applied to two symmetrically-located areas.Two weeks of treatment with clobetasol propionate produced a significantly greater decrease in total symptom score (combined scores of erythema, induration and scaling) than calcipotriol treatment (P0.0001). This improvement on the clobetasol propionate-treated side of the body was maintained throughout a subsequent 4-week treatment period when calcipotriol was applied to both sides of the body (P0.0001). The superiority of the clobetasol propionate followed by calcipotriol treatment was maintained during a 4-week, treatment-free, observation period. Treatments were well tolerated with no rebound effect.Clobetasol propionate ointment bd for 2 weeks followed by treatment with calcipotriol ointment bd for 4 weeks was superior to calcipotriol ointment alone in the treatment of plaque psoriasis.