Ambulatory care sensitive hospitalizations are a set of conditions for which access to effective primary care can reduce the likelihood of hospitalization. These hospitalizations have been used as an indicator of primary care performance in several countries and in three Brazilian states, but there is little consensus on which conditions should be included in this indicator. This paper presents a description of the steps undertaken to construct and validate a list for Brazil. The final list includes 20 groups of diagnostic conditions that represented 28.3% of a total of 2.8 million hospitalizations in the National Unified Health System in 2006. Gastroenteritis and complications, congestive heart failure, and asthma represented 44.1% of all ambulatory care sensitive hospitalizations. From 2000 to 2006, ambulatory care sensitive hospitalizations decreased by 15.8%, and this reduction was more significant than that observed in all other hospitalizations. The article concludes with potential applications and limitations of the proposed Brazilian list.