Tacrolimus 0.03% ointment is licensed for second-line treatment of children with atopic dermatitis (AD). Although data are available from clinical trials, no study has enrolled only second-line patients. This double-blind, non-inferiority study compared tacrolimus 0.03% and fluticasone 0.005% ointments in children with moderate-to-severe AD, who had responded insufficiently to conventional therapies. Children (aged 2-15 yr) were randomized to tacrolimus ointment (n = 240) or fluticasone ointment (n = 239), twice daily until clearance or for a maximum of 3 wk and, if lesions remained, once daily for up to 3 wk further. Primary end-point was week 3 response rate (improvement of >or=60% in modified Eczema Area and Severity Index and not withdrawn for lack of efficacy). Secondary end-points included pruritus and sleep quality, global assessment of clinical response, incidence of new flares and safety. Response rates were 86.3% with tacrolimus ointment and 91.5% with fluticasone. Lower limit of the 95% confidence interval was -11.8%, exceeding the non-inferiority limit of -15% and meeting the primary end-point. Moderate or better improvement on the physicians' global assessment occurred in 93.6% and 92.4% of patients in the tacrolimus ointment and fluticasone arms, respectively, while median pruritus scores improved by 84.0% and 91.5%. Sleep quality improved by approximately 92% in both treatment arms. After day 21, new flare-up occurred in 5.5% and 11.3% of patients receiving tacrolimus ointment and fluticasone, respectively; mean times to new flares were 6.5 +/- 5.0 and 8.6 +/- 5.2 days. Adverse events were similar between the two arms, with the exception of application-site skin burning sensation in the tacrolimus ointment group. In conclusion, efficacy of tacrolimus 0.03% ointment as second-line treatment was not inferior to that of fluticasone 0.005% ointment, with similar benefits on global disease improvement and quality of sleep.