This article summarizes the chapter on epidemiological surveillance of sexually transmitted infections (STI) that comprises the 2020 Clinical Protocol and Therapeutic Guidelines (PCDT) for Comprehensive Care for People with STI, published by the Health Surveillance Department of the Brazilian Ministry of Health. It presents some reflections on the new case definitions for surveillance of acquired syphilis, syphilis in pregnant women, and congenital syphilis. The 2020 PCDT-IST was elaborated grounded on scientific evidence and validated in discussions with specialists. Epidemiological and clinical aspects are addressed, and health service managers' guidelines regarding programmatic and operational management of these diseases are presented. Guidelines for health professionals on screening, diagnosing, and treating people with STI and their sex partners, in addition to strategies for surveillance, prevention, and control actions, are also published. sexually transmitted infections are among the most common diseases in the world. They affect people's health and life, impact reproductive and child health, contribute to infertility and complications during pregnancy and birth.