We conducted a randomized, double-blind, placebo-controlled trial to assess the atrophogenicity of tacrolimus ointment. In a combined group of atopic dermatitis patients (n = 14) and healthy volunteers (n = 12), 0.3% tacrolimus, 0.1% tacrolimus, betamethasone-valerate, and a vehicle control were applied in a randomized order to nonsymptomatic, 4 cm x 4 cm regions of abdominal skin. After 7 d of treatment under occlusion, the carboxy- and amino-terminal propeptides of procollagen I (PICP, PINP) and the amino-terminal propeptide of procollagen III (PIIINP) were measured from suction blister fluid with specific radioimmunoassays. In addition, ultrasound measurements of skin thickness were taken. Betamethasone-treated areas showed median PICP, PINP, and PIIINP concentrations of 17.0%, 17.6%, and 39.5% of the vehicle control at the end of the treatment period, respectively, whereas the 0.1% and 0.3% tacrolimus-treated areas showed median concentrations of approximately 100% of the vehicle control (p < 0.001). Betamethasone was also the only treatment to reduce skin thickness; the median decrease in skin thickness was 7.4% relative to 0.1% tacrolimus, 7.1% relative to 0.3% tacrolimus, and 8.8% relative to the vehicle control (p < 0.01). Results for atopic dermatitis patients and healthy volunteers were similar. These findings suggest that tacrolimus does not cause skin atrophy.