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Background The dose-response relationship between two dose levels of fluticasone/formoterol ( flutiform ® , 100/10 μg and 500/20 μg) was evaluated in asthmatic patients. Non-invasive inflammatory markers were used including adenosine monophosphate (AMP) challenge (primary endpoint), and sputum eosinophils and fractional exhaled nitric oxide (FeNO) (secondary endpoints). Methods Patients aged ≥18 years with forced expiratory volume in 1 s (FEV 1 ) ≥60% predicted and who required a dose of <60 mg AMP to elicit a 20% drop in FEV 1 (AMP PD 20 ) were randomised in this incomplete block, crossover study to receive 2 of 3 treatments b.i.d.: fluticasone/formoterol 500/20 μg (high dose), 100/10 μg (low dose) or placebo, during 2 periods of 28 ± 3 days each, separated by 2–3 weeks. AMP challenges were performed pre-dose and 12 h after last dose at the end of each treatment period. A series of post hoc analyses were performed only in patients allocated to both fluticasone/formoterol doses, who completed the study and had evaluable AMP PD 20 data for both treatments (“fluticasone/formoterol subgroup”). Changes in AMP PD 20 FEV 1 , percentage sputum eosinophils and FeNO levels (Day 1 vs Day 28) between treatments were compared by an analysis of covariance (ANCOVA). Results Sixty-two patients were randomised and 46 completed the study. Fifteen patients received both high- and low-dose fluticasone/formoterol ( post hoc subgroup). The difference in AMP PD 20 for the overall population was not statistically significant between high- and low-dose fluticasone/formoterol (LS mean fold difference: 1.3; p = 0.489), although both dose levels were superior to placebo: high-dose vs placebo LS mean fold difference: 4.4, p < 0.001; low-dose vs placebo LS mean fold difference: 3.5, p < 0.001. In the post hoc subgroup, the difference in AMP PD 20 between the doses was statistically significant in favour of the high-dose (LS mean fold difference: 2.4, p = 0.012). Other inflammatory parameters (sputum eosinophil counts and FeNO) showed small differences and statistically non-significant changes between high- and low-dose fluticasone/formoterol. Conclusions A significant dose-response was found between low- and high-dose fluticasone/formoterol in the post hoc subgroup (patients who received both doses), but not in the overall population, with the higher dose demonstrating a greater reduction in airway responsiveness to AMP. [ABSTRACT FROM AUTHOR]