Background Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN)are acute mucocutaneous reactions associated with poor prognosis. The treatment is mainly symptomatic, based on supportive care. Until now, several curative treatments have been proposed without evidence of effectiveness.Objectives To evaluate the effect of ciclosporin on SJS and TEN after a short series had suggested a benefit.Methods We conducted an open, phase II trial to determine the safety and possible benefit of ciclosporin. Among the 45 consecutive patients admitted for SJS /TEN from March 2005 to September 2007, 29 fulfilled inclusion criteria. Ciclosporin was administered orally (3 mg kg)1 daily for 10 days) and tapered over a month. Clinical and biological evaluations were performed sequentially. Predicted death rate was estimated with a validated prognostic score (SCORTEN).Results Twenty-nine patients were included at a mean +/- SD of 2.8 +/- 1.8 days after onset. The final diagnosis was SJS (n = 10), SJS ⁄TEN overlap (n = 12) and TEN(n = 7). One month of treatment was completed in 26. Ciclosporin was stopped after more than 10 days in three cases for side-effects including posterior leucoencephalopathy (n = 1), neutropenia (n = 1) and nosocomial pneumopathy(n = 1). Ciclosporin dosage was tapered earlier than scheduled in two cases for alteration in renal function. The prognostic score predicted 2.75 deaths; none occurred (P = 0.1). Mean epidermal detachment remained stable in 18 of 29 cases (62%). The mean ± SD hospital stay was 16.2 +/- 9.1 days.Conclusions Both the death rate and the progression of detachment seemed lower than expected, suggesting a possible usefulness of ciclosporin in SJS and TEN that needs to be confirmed.