Cyclosporine A (CsA) effectively controls psoriasis, however, its long-term continuous use is not recommended. This study aims to evaluate the efficacy and tolerability of week-end CsA microemulsion for the reduction of relapse rate in patients with chronic plaque psoriasis who had achieved clinical remission following continuous CsA therapy. The PREWENT (Psoriasis Relapse Evaluation with WeekEnd Neoral Treatment) study was a 24-week, randomized, double-blind, multicenter study, carried out in 22 Italian hospital or university Dermatology units. CsA was discontinued for 8 days previous to the patients being randomized to oral CsA 5 mglkglday or placebo for two consecutive days/week, for a total period of 24 weeks. The primary endpoint was clinical success rate at week 24, defined as the proportion of patients with no clinical worsening (no relapse or a Psoriasis Area and Severity Index [PASI] <75% of pre-treatment PASI). A total of 162 patients were randomized to CsA and 81 to placebo. Clinical success rates at 24 weeks were 66.9% and 53.2% with CsA and placebo, respectively (p = 0.072). Time to first relapse was significantly prolonged with CsA versus placebo (p = 0.023), and PASI was significantly lower from weeks 4 to 16 in CsA recipients. In patients with moderate-severe psoriasis, the clinical success rate was significantly increased with CsA compared to placebo (69.9% vs 46.3%; p = 0.011), and significantly lower increases in PASI were observed from week 4 to week 24 (p < 0.05 vs placebo). CsA was well tolerated, with no differences in mean blood creatinine or blood pressure between CsA and placebo recipients. However, the high withdrawal rate (22.2% of randomized patients), which was not related to side effects, may have led to an overestimation of efficacy, but the study had a good statistical power (88% greater than that observed in similar studies, i.e, 80%). Week-end CsA administration was shown to prolong safely and effectively the time to first relapse in psoriasis patients.Psoriasis is an inflammatory skin condition characterized by chronic recurrent course. T-cell activation and cytokine production playa key role in the formation of skin lesions (1-2). In most patients, the immunosuppressive drug cyclosporine A (CsA) is effective in improving plaque psoriasis (3). The microemulsion formulation of CsA is approved for the treatment of severe psoriasis, when conventional topical treatments are ineffective or inappropriate. The efficacy of CsA microemulsion in psoriasis has been demonstrated in several randomized, controlled clinical trials, with different dosage regimens (4-6).