INTRODUCTION:
The Southeast region of Brazil concentrates the largest private health care providers and the highest levels of public health investment, including resources allocated to Primary Health Care (PHC) delivered through health units.¹ As the main entry point to the Unified Health System (SUS), PHC addresses social inequalities and promotes health and disease prevention through multiprofessional teams at the territorial level.² This study aims to describe the implementation of health units in the capitals of the Southeast region of Brazil.

METHODS:
This qualitative study was conducted through the collection of records of health facilities registered in the National Registry of Health Establishments (CNES) ³ and classified as health units in the capitals of the Southeast region. Data were organized in Microsoft Excel according to type of establishment (health unit), quantity, and year of registration. Data collection took place in December 2024 in Vitória and Rio de Janeiro, and in March and April 2025 in Belo Horizonte and São Paulo, respectively.

RESULTS:
In Vitória, Rio de Janeiro, Belo Horizonte, and São Paulo, 30, 245, 153, and 484 active Basic Health Units (BHUs) were identified, respectively. All units were registered under public administration, with no distinction between direct management by municipal health departments and indirect management through outsourcing. The implementation of BHUs began in 2001. Peak implementation occurred in 2003 in Vitória, when 70% of units were established. In Rio de Janeiro, implementation was more dispersed, with 13% in 2001, 12% in 2002, and 13% in 2016. In Belo Horizonte, 76% of units were established in 2002, while in São Paulo, 75% were implemented in 2003.

CONCLUSIONS:
The expansion of Basic Health Units was concentrated in the early phase of the Unified Health System (SUS), and limitations in data on management models underscore the need for greater transparency and further analysis.