This study analyses how political and institutional factors affected the performance of municipalities in improving social welfare in Brazil in the period from1990 to 2000. Themodel adopts a stochastic production frontier, conditioned by variables related to the provision costs of services and those that can affect municipal efficiency. The results indicated that we can not reject:1) economies of scale; 2) the effect of vote margin in the municipality and the type (first or second) of mandate of elected governor, which indicates a form of patronage; and 3) that local politics and the existence of sectorial boards did not affect the level of efficiency for municipal spending, suggesting an asymmetry of information between politics and voters.