The present review aims to identify and summarize epidemiologic investigations published during 2011 on the environmental risk factors for asthma. Potentially eligible papers were identified by a MEDLINE search. In total, 1,130 items were retrieved. Based on a broad definition of environment, the following topics were included: obesity, diet, vitamin D, air pollution, farming environment, and social factors. Some of the more relevant contributions included evidence that 1) obesity precedes asthma, 2) fruit consumption is longitudinally associated with a lower risk of asthma and atopy, 3) a comprehensive statewide smoking ban was followed by a reduction in hospital admissions for asthma, 4) asthma is one of the diseases showing the largest burdens due to environmental tobacco smoke, 5) traffic-related urban air pollution is associated with bronchial inflammation as measured by fractional exhaled nitric oxide and uncontrolled asthma, 6) aeroallergens and desert dust may contribute to the short-term effects of air pollution and asthma, and 7) maternal exposure to air pollution before and during pregnancy may alter the immune competence in offspring.