OBJECTIVE: The objective of this systematic review was to assess the effectiveness of yoga as a treatment option for asthma. METHOD: Seven databases were searched from their inception to October 2010. Randomized clinical trials (RCTs) and non-randomized clinical trials (NRCTs) were considered, if they investigated any type of yoga in patients with asthma. The selection of studies, data extraction, and validation were performed independently by two reviewers. RESULTS: Six RCTs and one NRCT met the inclusion criteria. Their methodological quality was mostly poor. Three RCTs and one NRCT suggested that yoga leads to a significantly greater reduction in spirometric measures, airway hyperresponsivity, dose of histamine needed to provoke a 20% reduction in forced expiratory volume in the first second, weekly number of asthma attacks, and need for drug treatment. Three RCTs showed no positive effects compared to various control interventions. CONCLUSIONS: The belief that yoga alleviates asthma is not supported by sound evidence. Further, more rigorous trials are warranted.