Pimecrolimus cream 1%, a nonsteroid inhibitor of inflammatory cytokines, offers an alternative to corticosteroids in the treatment of atopic dermatitis. Here we evaluate pimecrolimus blood concentrations and tolerability to pimecrolimus cream 1% in 22 infants below 2 years of age with atopic dermatitis (10-92% body surface area affected at baseline). Efficacy was assessed as a secondary objective. Pimecrolimus cream 1% was applied twice daily for 3 weeks. Blood concentrations were low, typically (96% of total 100 concentrations measured) below 2 ng/mL, the majority (71%) remaining below 0.5 ng/mL. The highest concentration observed was 2.26 ng/mL. At steady state, there was no indication of accumulation. Pimecrolimus was well tolerated locally and systemically, with no serious adverse events recorded. Most adverse events recorded (35 in 17/22 patients) were typical of the young pediatric population studied, of mild to moderate severity, and not considered to be study-medication related, with the exception of four local adverse effects limited to the site of cream application. No clinically relevant change was observed in physical examination, vital signs, or laboratory safety parameters. A rapid onset of therapeutic effect was observed within the first four days of treatment. Pimecrolimus cream 1% is well tolerated in infants 3 to 23 months of age treated for 3 weeks, and results in minimal systemic exposure.