This article aims to evaluate the degree of competition in the dairy industry, in the relevant markets of Ultra High Temperature (UHT) milk and pasteurized milk, by means of price transmission and marketing margin behavior. The empirical analysis is based on the model formerly proposed by Houck (1977) and latter detailed by Carman and Sexton (2005).This model analyzes separately the effects of input price increases and reductions on consumer prices, allowing for estimations of price transmission and margin behavior. Cepea-USP and Fipe provide, respectively, weekly input prices and consumer prices, both for the period of December 1999 to December 2005. As a major result, the degree of competition in the UHT relevant market was found to be robustly different from the pasteurized milk market. Whereas in the first price transmission corroborates the hypothesis of competitive market, in the pasteurized milk market there is evidence of imperfections both in price transmission and margin behavior. The outstanding increase of UHT milk consumption has fostered competition and liquidity in the dairy industry and milk distribution, allowing for faster price transmission throughout the production chain. Nevertheless fixed markup pricing found in the UHT relevant market shows that dairy industry and milk distribution have some degree of market power so as nominal changes in input prices are passed through consumers in a larger magnitude.