Tacrolimus (FK506) ointment is widely used in the treatment of patients with atopic dermatitis. The drug exerts its action by down-regulating antigen-specific T-cell activities and associated proinflammatory cytokine production. A number of clinical studies have evaluated the efficacy and safety of 0.1% tacrolimus ointment compared with vehicle or topical corticosteroids in adult patients with atopic dermatitis. These studies have suggested that topical tacrolimus has a rapid onset of action and exerts sustained therapeutic effects, with an efficacy similar to that of moderate to potent topical corticosteroids, but without causing skin atrophy. Two phase III randomised, controlled clinical trials have been conducted in Japanese adult patients with atopic dermatitis to compare the efficacy and safety of topical 0.1% tacrolimus with topical corticosteroid ointments. In the first study, patients with moderate or severe atopic dermatitis on the trunk and extremities were randomised to 3 weeks of treatment with topical 0.1% tacrolimus or the mid-potency topical corticosteroid 0.12% betamethasone valerate. Over 90% of the patients in each study group experienced at least a moderate improvement at the end of the study. In the second study, patients with moderate or severe atopic dermatitis on the head or neck were randomised to 1 week of treatment with 0.1% tacrolimus or the mild-potency corticosteroid 0.1% alclometasone dipropionate. Significantly greater improvements in individual symptom scores were observed with topical tacrolimus compared with alclometasone dipropionate, with overall global improvement at 1 week being statistically superior with tacrolimus. Furthermore, in a long-term open-label study involving 568 patients, at least a moderate global improvement in symptoms was observed in 85% of patients at 6 weeks, increasing to 91% at both 26 weeks and 52 weeks; this rate was maintained throughout the 2-year duration of the study. 0.1% tacrolimus ointment was considered to be safe in the majority of patients. The most prevalent adverse reactions were local application site irritations, which generally resolved with continued therapy. In summary, these findings suggest that 0.1% tacrolimus ointment is an effective and safe nonsteroidal alternative therapy for adult patients with atopic dermatitis.