Previous cross-sectional studies could establish an association between prevalence of self-reported wheeze and urban-rural environment, but the impact of urbanization on meaningful outcomes of asthma for public health is not established yet. Objectives: Evaluate the effect of urbanization on asthma burden. Methods: A time series study of 5,505 Brazilian municipalities. The unit of analysis was the municipality. Two time frames were evaluated: from 1999 to 2001 and from 2009 to 2011. Trends from the first to the second time frame were evaluated. Governmental databases were the source of information. Multivariate binary logistic regression models were used. Results: In the age range from 5 to 24 years old, municipalities with increase in the proportion of individuals living in urban area had lower odds to reduce hospital admission rate from asthma (OR: .93) and lower odds to reduce death rate from asthma (OR: .88). In the age range from 25 to 39 years old, municipalities with increase in the proportion of individuals living in urban area had lower odds to reduce hospital admission rate from asthma (OR: .93) and lower odds to reduce death rate from asthma (OR: .82). Municipalities that increased access to physicians and that supplied inhaled corticosteroids free of charge for asthma since year 2003 had increased odds to reduce hospital admission and death rates from asthma. Conclusions: Increase in urban population was associated with lower odds to reduce hospital admission and death rates from asthma in children and young adults living in a transition society.