The effectiveness of inhaled corticosteroids (ICS) in patients with chronic obstructive pulmonary disease (COPD) remains controversial. Randomized controlled trials, meta-analyses, medication withdrawal studies, and observational reports have examined this question, with mixed results. Observational studies have been subject to criticism because of study design involving immortal time bias. Some randomized controlled trials suggest small benefits in lung function and health status, and a reduction in the rate of acute exacerbations of COPD and mortality, but their incomplete follow-up and statistical methods have been criticized. The greatest benefits of ICS in COPD have been reported with use of ICS and long-acting beta-agonist combination therapy, although no benefit was found for the primary outcome studied under the most rigorous methodology by the recent TORCH and Optimal randomized trials. Thus, although future randomized trials will need to be conducted with the most rigorous methodology for all outcomes, much uncertainty remains regarding the potential benefits of ICS in COPD.