INTRODUCTION The goal of this retrospective study was to evaluate the effects of cyclosporin A on renal function in patients treated for five years or more. PATIENTS AND METHODS Two hundred twenty-four psoriasis patients were treated with cyclosporin at St. Louis Hospital, in Paris, from 1988 to 1997. Eleven patients (5 p. 100 of the total) took cyclosporin for at least five years. Nine case histories were available for the analysis. RESULTS The group studied consisted of eight men and one woman, ranging in age from 28 to 48 with an average age of 38 years. The average cyclosporin dosage was 3.6 mg/kg/day (2.0-5.0 mg/kg/day). The changes in renal function were not significant as compared to the baseline level. The patients did not show persistent increases of serum creatinine more than 30 p. 100 of the pre-treatment value. Two patients had to discontinue treatment after 6 years because of a 20 p. 100 decrease in glomerular filtration rate. DISCUSSION Previous studies have shown that cyclosporin A is not a suitable long-term continuous monotherapy for psoriasis. However, with precise and regular monitoring of kidney function, a minority of patients can benefit from prolonged treatment without experiencing side effects.