Airway hyperresponsiveness induced by adenosine-5'-monophosphate (AMP) is regarded as a reliable model for allergic asthma and for the evaluation of anti-asthmatic drugs. Single-dose inhaled corticosteroids (ICS) are known to be protective in this model, but the duration of action of these drugs in this model has never been studied. The duration of ICS protection was determined by administration of single-dose fluticasone propionate (FP; 1,000 micrograms) up to 26 h before AMP challenge. A randomised, double-blind, placebo-controlled, four-way crossover study was performed in 13 mild asthmatics (mean +/- SD predicted forced expiratory volume in one second (FEV1) 98 +/- 7%). Each subject received placebo and FP (at 26, 14 or 2 h prior to the AMP challenge). Furthermore, the marker exhaled nitric oxide (eNO) was studied after administration at these time points to investigate whether eNO also demonstrates the duration of action of ICS. The doubling concentrations difference (DCD) of AMP causing a 20% fall in FEV1, when FP was administered 26, 14 or 2 h prior to challenge, was significantly increased as compared with placebo: DCD (95% confidence interval) at 26 h, 0.73 (0.20-1.26), p = 0.008; 14 h, 1.50 (0.99-2.01), p < 0.001; and 2 h, 2.89 (2.37-3.40), p < 0.001. However, eNO was not significantly affected at these time points. In conclusion, a single dose of 1,000 micrograms inhaled fluticasone propionate protects against adenosine-5'-monophosphate airway hyperresponsiveness up to 26 h after dosing. This study suggests that adenosine-5'-monophosphate challenge can be used as a sensitive marker to study the duration of action of inhaled corticosteroids.