MENTAL HEALTH AND PRIMARY CARE: THE ROLE OF DIAGNOSIS IN THE CONSTRUCTION OF CARE FOR AUTISTIC CHILDRENautism; mental health; primary care; psychiatric diagnosisSince Leo Kanner proposed autism as a nosographic category in psychopathologies, the understanding of this disorder has undergone significant changes. With the changes in the fourth edition of the DSM, the diagnosis of autism has become alarmingly more popular, resulting in a significant increase in its incidence. This popularization has generated tensions over the possible existence of a false epidemic, influenced by changes in psychiatry and by cultural, material and economic factors, affecting both the public and private sectors. Within the scope of the Unified Health System, several public services have emerged aimed exclusively at treating children with Autism Spectrum Disorder (ASD), although these services often deviate from the guidelines established for the Child and Adolescent Mental Health policy. This study aims to investigate and understand the uses and meanings of the diagnosis of Autism Spectrum Disorder (ASD) in children treated at primary health care units in the city of Rio de Janeiro. For this, we will use a qualitative methodology, employing the content analysis technique. The data to be analyzed will be collected through documentary analysis and semi-structured interviews. The documentary analysis will cover the medical records of patients registered in the Regulatory System (SISREG-RJ) for Multiprofessional Assessment, specifically those with suspected autism, considering the technical note SMS-OFI-2023/32745 of 09/12/2023. The data to be analyzed refer to the period from 01/01/2024 to 12/01/2024. The interviews will be conducted with medical professionals and nurses from Family Health in the Basic Health Units, in order to understand the meanings and uses of the diagnosis in the process of caring for children with suspected or diagnosed ASD. We hope that the results obtained will contribute to the field of childhood, psychology and public health, by allowing a deeper understanding of how diagnostic assessment is carried out in the care of this public.