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Randomized controlled trials, known as efficacy trials and long considered the gold standard for evidence-based asthma guidelines, are designed to test whether interventions have a benefit for selective patient populations under ideal conditions. The goal of pragmatic trials and observational studies instead is to understand real-life efficacy, known as effectiveness. This review summarizes the strengths and limitations of efficacy and effectiveness trials, results of recent effectiveness trials in asthma and initiatives promoting effectiveness research.Recent pragmatic trials and observational studies have examined outcomes of interventions for diverse real-life patient populations, including smokers and patients with variable adherence, inhaler technique and baseline asthma control. Study results challenge practice guidelines regarding relative effectiveness of leukotriene receptor antagonists and inhaled corticosteroids (ICS); supplement guidelines with regard to effectiveness of interventions in smokers; and begin to address gaps in guidelines regarding choice of ICS and inhaler device. Initiatives are ongoing to refine methods of observational research and to harmonize asthma outcomes for better integration of results from all types of trials.Results of pragmatic trials and observational studies are an important component of the evidence needed to inform guideline recommendations and decision-making by healthcare providers, patients and policymakers.