Atopic dermatitis (AD) is a chronic inflammatory skin disease frequently associated with asthma, rhinitis, and food allergy. Lymphocytes producing Th2-type cytokines (such as interleukin [IL]-3, IL-4, and IL-5) have been thought to have a key role in the pathogenesis of the disease. We have recently demonstrated that elevated serum levels of the soluble form of CD30 (sCD30), an activation marker of Th2-cell clones, correlates with disease activity in pediatric patients suffering from AD. Clinical trials have demonstrated that cyclosporin A (CyA) treatment resulted in significant improvement of clinical symptoms in patients affected with AD. In this study, we evaluated the role of CyA in modulating sCD30 release in a group of adult patients affected by severe AD treated with CyA at the dosage of 3.5 mg/kg body weight for 12 weeks. Our results demonstrated, in parallel with an improvement of clinical symptoms, a significant reduction of serum levels of both IL-4 and sCD30, thus suggesting that CyA can prevent the activation of Th2 cells observed in AD.