The efficacy and tolerability of fluticasone propionate (FP) 2 mg daily via a metered-dose inhaler and Volumatic (Glaxo Wellcome) spacer device was compared with nebulized budesonide (nBUD), 2 and 4 mg daily, in a multi-centre, open-label, cross-over study of adult asthmatics. Patients received, in random order, either 4 weeks of treatment with FP followed by 4 weeks of treatment with nBUD, or vice versa, with an intervening 4 week 'wash-out' period between treatments. Thirty patients completed the study, of whom 24 were evaluable. In terms of the primary efficacy parameter, change in mean morning peak expiratory flow (PEF) (l min-1) from baseline to the fourth week of each treatment period, FP was more effective than nBUD [mean difference (FP-nBUD) 21.1 l min-1, P = 0.007, 95% CI (6.5, 35.7)]. Sub-group analysis demonstrated FP to be superior to the 4 mg nBUD [mean treatment difference (FP-nBUD) 42.9 l min-1, P = 0.026, 95% CI (7.1, 78.8)] and at least as efficacious as the 2 mg nBUD sub-group [mean treatment difference (FP-nBUD) 10.2 l min-1, P = 0.211, 95% CI (-6.5, 26.9)]. Furthermore, larger reductions in diurnal variation were observed during FP treatment [mean treatment difference (FP-nBUD) -4.4 percentage points, P = 0.028, 95% CI (-8.4, -0.5)]. There was no significant difference between the treatments for the proportion of symptom-free 24 h periods. Of those expressing a preference, significantly more patients found FP via a metered-dose inhaler and spacer device both easier to administer (78%, P = 0.007) and more convenient to take (76%, P = 0.008) than nebulized budesonide. In addition, cost per patient analysis showed that nebulized budesonide was from 1.7 to 3.5 times more expensive than FP.