The response in asthmatic young children to inhaled steroids within the usual pediatric dose range is unknown. We therefore evaluated the dose-related response in young children with moderate asthma to inhaled fluticasone propionate (FP) (delivered via the Babyhaler spacer device) within the pediatric dose range. A total of 237 children (mean age 28 mo, range 12 to 47) with moderate asthmatic symptoms were studied in this multicenter, randomized, double-blind, parallel group, placebo-controlled study of 12 wk treatment following a 4-wk run-in period. The median use of rescue medication was 1 dose in 2 d during the run-in period. FP 50 micrograms twice daily (FP100) and 100 micrograms twice daily (FP200) was compared with placebo inhaled from a pressurized metered-dose inhaler (pMDI) and the Babyhaler spacer device. With FP200 there was a statistically significant improvement from baseline, as compared with the placebo group, in 8 of 10 diary card parameters, including the three symptom domains of wheeze, cough, and breathlessness, and use of rescue medication. FP100 produced a significant reduction in 5 of these 10 parameters, whereas no significant differences were found between the FP200 and FP100. The numbers of patients with at least one exacerbation during treatment with placebo, FP100, and FP200 were 37%, 26%, and 20%, respectively. This difference between placebo and FP200, as well as the dose-related order was significant (p < 0.05). Both FP doses were as well tolerated as placebo over the 12 wk treatment with a similar incidence of adverse effects. Asthmatic symptoms in 1- to 3-yr-old children responded in a significant and dose-related manner to treatment with FP within a pediatric dose range.