Context:Thalidomide use in cutaneous sarcoidosis is based on data from small case series or case reports. Objective:To evaluate the efficacy and safety of thalidomide in severe cutaneous sarcoidosis. Design, Setting and Participants:Randomized, double-bind, parallel, placebo-controlled, investigator-masked, multicentre trial lasting 3 months, and an open-label study from month 3 to month 6. Adults with clinical and histological diagnosis of cutaneous sarcoidosis were included in nine hospital centres in France. Intervention:Patients were randomized 1:1 to oral thalidomide (100 mg once daily) or to a matching oral placebo for three months. In the course of an open-label follow-up from month 3 to month 6, all patients received thalidomide 100 mg to 200 mg daily. Main outcome measures:The proportions of patients with a partial or complete cutaneous response at month 3, based on at least a 50% improvement of 3 target lesions scored for area and infiltration, were compared across randomisation groups. Results:The intent-to-treat population included 39 patients. None of them had a complete cutaneous response. Four out of 20 patients (20%) in the thalidomide group vs 4 out of 19 patients in the placebo group (21%) had a partial cutaneous response at month 3 (difference in proportion of -1% (95% CI -26% to +24%) for thalidomide vs placebo; p=1.0). Eight patients with side effects were recorded in the thalidomide group vs 3 in the placebo group. We observed a large number of adverse event-related discontinuations in patients under thalidomide in the first 3 months (4 patients with thalidomide, 0 with placebo), and in the 3 following months (5 patients). Conclusion:At a dose of 100 mg daily for 3 months, our results do not encourage thalidomide use in cutaneous sarcoidosis. Trial registration:NCT0030552 (ClinicalTrial.gov). Context: Thalidomide use in cutaneous sarcoidosis is based on data from small case series or case reports. Objective: To evaluate the efficacy and safety of thalidomide in severe cutaneous sarcoidosis. Design, Setting and Participants: Randomized, double-bind, parallel, placebo-controlled, investigator-masked, multicentre trial lasting 3 months, and an open-label study from month 3 to month 6. Adults with clinical and histological diagnosis of cutaneous sarcoidosis were included in nine hospital centres in France. Intervention: Patients were randomized 1:1 to oral thalidomide (100 mg once daily) or to a matching oral placebo for three months. In the course of an open-label follow-up from month 3 to month 6, all patients received thalidomide 100 mg to 200 mg daily. Main outcome measures: The proportions of patients with a partial or complete cutaneous response at month 3, based on at least a 50% improvement of 3 target lesions scored for area and infiltration, were compared across randomisation groups. Results: The intent-to-treat population included 39 patients. None of them had a complete cutaneous response. Four out of 20 patients (20%) in the thalidomide group vs 4 out of 19 patients in the placebo group (21%) had a partial cutaneous response at month 3 (difference in proportion of -1% (95% CI -26% to +24%) for thalidomide vs placebo; p=1.0). Eight patients with side effects were recorded in the thalidomide group vs 3 in the placebo group. We observed a large number of adverse event-related discontinuations in patients under thalidomide in the first 3 months (4 patients with thalidomide, 0 with placebo), and in the 3 following months (5 patients). Conclusion: At a dose of 100 mg daily for 3 months, our results do not encourage thalidomide use in cutaneous sarcoidosis. Trial registration: NCT0030552 (ClinicalTrial.gov).