In two randomized, double-blind, multicenter studies, a total of 631 adult patients with moderate to severe atopic dermatitis applied tacrolimus ointment (0.03% or 0.1%) or vehicle twice daily for up to 12 weeks. The mean percent body surface area (%BSA) affected at baseline was 45%, and 56% of patients had severe atopic dermatitis. As previously reported, these studies showed that tacrolimus ointment was superior to vehicle for all efficacy parameters measured. This report focuses on the safety of tacrolimus ointment in these studies. The most common adverse events were the sensation of skin burning, pruritus, flu-like symptoms, skin erythema, and headache. Skin burning and pruritus were more common among patients with severe or extensive disease; these events were usually brief and were resolved during the first few days of treatment. Common adverse events with a significantly higher incidence in one or both of the tacrolimus ointment groups than in the vehicle group included skin burning, flu-like symptoms, and headache. More patients in the vehicle group discontinued the study because of an adverse event than in either of the tacrolimus ointment groups. There were no notable or consistent changes in any laboratory variables. Tacrolimus was not detected in 80% of blood samples collected. Measurable concentrations of tacrolimus were transitory and were not associated with adverse events. Tacrolimus ointment is a safe therapy for the treatment of adult patients with atopic dermatitis on the face, neck, or other body regions.