The aims of this study were to determine the efficacy, safety and tolerability of a new, microemulsified, oral formulation of cyclosporin (Neoral R ) in chronic plaque psoriasis. Subjects were adults with moderate to severe chronic plaque psoriasis requiring hospital-based treatment. Cyclosporin 5 mg/kg/day, was given until remission (90% reduction in area of skin affected) or for a maximum of 12 weeks. Disease severity was recorded at baseline using the PASI and was monitored by estimating the percentage of total skin surface affected, and sign scores for erythema, infiltration and desquamation. Treatment response and tolerability were also assessed by subjects using five point scales.Thirty-eight subjects were treated, mean age 37 years, mean baseline PASI was 12.6, range 4-36. Mean treatment duration was 48 days. Mean percentage of skin affected improved from 18 (SD 16.9) at baseline to 1.3 (1.8) at the end of treatment (n = 38). Remission was achieved in 29 subjects. Thirty-seven considered they had shown a considerable improvement or complete response. Although 138 adverse events were reported by 36 subjects, in only 3 was treatment discontinued as a result and 32 graded tolerability as good or very good. Transient increases in creatinine of more than 30% were seen in 7 subjects.