Background : Multiple immunologic abnormalities such as impaired T-cell function, elevated serum IgE level, and increased interleukin 4 production have been demonstrated in patients with atopic dermatitis. Objective : As part of a 12-week, multicenter, double-blind, placebo-controlled clinical trial, we evaluated the safety and efficacy of thymopentin (Timunox) as an adjunctive treatment in patients with severe atopic dermatitis. Methods : Thirty-nine patients at least 2 years old with severe atopic dermatitis on a minimum of 20% of their cutaneous surface area were randomly selected to receive either thrice-weekly subcutaneous injections of thymopentin, 50 mg, or placebo. Use of triamcinolone 0.1% or hydrocortisone 1.0% cream and oral antihistamines were permitted during this trial. Results : After 12 weeks, thymopentin-treated patients had significantly greater improvement than those receiving placebo. No thymopentin-related adverse events occurred. Conclusion : Thymopentin may be a safe effective adjunct to therapy in patients with severe atopic dermatitis.