BACKGROUND Seborrheic dermatitis, an inflammatory dermatosis that principally affects sebaceous areas, may be related to the presence of the yeast Pityrosporum ovale. Topical therapy with corticosteroids, although in general effective, may be associated with several unwanted effects. The development of alternative non-steroid-based therapies may enable patients to avoid the use of topical steroids and help elucidate the pathogenesis of the disease. OBJECTIVE This study aimed to assess the efficacy and safety of an ointment containing 8% lithium succinate in the treatment of seborrheic dermatitis. METHODS The study consisted of a multicenter placebo-controlled clinical trial in 227 adult patients. RESULTS Lithium succinate ointment was significantly more effective than placebo in treating all the symptoms of seborrheic dermatitis. No specific unwanted effects were associated with its use. Relapse was slow when treatment was stopped. CONCLUSIONS The effectiveness of lithium succinate ointment in the treatment of seborrheic dermatitis adds to the evidence implicating P. ovale in the pathogenesis of that condition.