Abstract : The Brazilian Amazonia, detaining a vast biodiversity, has undergone great transformations in the economic, social, cultural and ecological aspects. The Transamazonica (Brazilian Highway 230 Region) distinguishes by the great participation of the family agriculture, in terms of occupied area, population and food production. It is characterized by a diverse system of production, where cattle breeding and dairy takes a strategic role as a food source to the families, generating income by selling of milk and calf. In this context, cattle breeding have been suffering substantial changes in its system of milk production, and in its productive chain. The aim of this study is to understand how the family agriculture establishments of milk systems work in the Eastern Brazilian Amazonia frontier, in the municipality of Brasil Novo (state of Pará). A methodological arrangement has been used combining interviews with farmers and key informants, retroactive analysis over the importance of the milk in its way to the establishments, typologies of the establishments in 2001 and 2009, besides the empirical knowledge acquired throughout the fifteen years of research-development in the region. The results have shown a spectrum of evolution in the milk establishments, where two types of producers distinguishes, that we have named "Opportunistic Type" and "Persistent Type". Due to both inside and outside establishment factors, there is a constant fluctuation throughout this spectrum. Among these factors, the market access is fundamental, and it greatly defines the orientation that the producers follow when conducting their milk systems. The chain of milk production still shows concern. The direct producer-consumer trade in still a usual practice. The milk-processing factories are of small capacity, with disperse collective capacity radius, presenting a history of instability in their process. The precarious infrastructure in both the road system and electricity are key factors to explain the timid increase in the chain production structure in this region. These aspects take to a high degree of insecurity to most farmers, preventing them from investing in the activity, even with the low cost of the milk production. These deficiencies might have been resolved with adapted public policies, as well as by the strong increase of the local market, due to the Belo Monte Hydroelectric Dam construction.