Two patients with severe atopic dermatitis unresponsive to conventional therapy were enrolled in a clinical trial on thymostimulin (TP-1). TP-1 was administered by subcutaneous injection 1 mg/kg/day for 14 days and then 1 mg/kg/day on alternate days for 2 months. Clinical and immunological status were evaluated at baseline and at regular intervals during the treatment. Clinical severity scores included eight skin conditions (erythema, edema, vesicle, crust, excoriation, scaling, lichenification, pigmentation), two subjective components (itchiness and loss of sleep), and extent of area affected. There was a statistically significant improvement in the overall assessment of the severity scores. There were no definite changes in immunological parameters including CD4, CD8 T-cell subpopulations and serum IgE, but eosinophil count showed a mark decrease in one case. No serious side effects were observed.