The Longitudinal Cohorts Unit at IDI was established to consolidate all observational studies under one umbrella, ensuring uniformity and quality of data, and enforcing compliance with ethical standards and standard operating procedures for analysis and publication. The unit’s primary role is to ensure that IDI’s care and treatment platforms generate high-quality data for cohort analysis, which can answer clinical and operational questions relevant to national and regional HIV/AIDS care needs. The institute’s cohorts encompass over 70,000 patients with routinely collected electronic HIV prevention, care, and treatment data, covering both ART active and naïve patients as well as rural and urban populations. Additionally, sub-cohorts have been created to collect additional data on special groups of interest, such as HIV-positive young adults, HIV-positive pregnant mothers, HIV patients co-infected with tuberculosis, Kaposi’s sarcoma, and patients in discordant relationships. The unit has a dedicated team for quality assurance and quality control. In 2011, the unit was recognized as an African Network for Drugs and Diagnostic Innovations (ANDI) Centre of Excellence in Epidemiology of Infectious Diseases through a competitive, criteria-based process.