The Smoking Modulates Outcomes of Glucocorticoid Therapy in Asthma (SMOG) study was a randomized, double-blind, cross-over study, which compared the effect of inhaled corticosteroid treatment delivered twice daily for 8 weeks in the following two groups of patients with persistent asthma: 1) smokers; and 2) non-smokers. Smokers and non-smokers were matched into pairs according to gender and FEV1 status prior to the run-in period. Each member of the matched pair was randomized together to the same crossover sequence. There were 96 patients ages 18 to 35. The primary outcome was change in pre-bronchodilator FEV1 over the 8-week treatment period in smokers compared with non-smokers. Secondary outcomes were AM and PM PEF, PC20 methacholine, and markers of inflammation in induced sputum. A secondary comparison examined the effect of 8 weeks of treatment with a leukotriene receptor antagonist in asthmatics who smoked to those who did not. An additional analysis compared the response to inhaled corticosteroid with the response to leukotriene receptor antagonist. The study was completed and results have been submitted to a journal for publication.