A controlled clinical study was conducted on 6 patients with atopic dermatitis to assess the efficacy of transfer factor. After the code was broken the 3 patients treated with placebo preparation were treated with transfer factor for a further period of 10 weeks. No definite therapeutic effects could be demonstrated. The immunological in vivo and in vitro tests failed to reveal any effects except for a change to positive in the tuberculin skin test in those patients who had previously been skin test negative. The treatment had to be discontinued in one patient due to a suspected allergic reaction against transfer factor.