ObjectivesRapid initiation of antiretroviral therapy (ART) engenders faster viral suppression but with suboptimal rates of durable viral suppression and engagement in care, as reported by clinical trials in resource-limited settings. Real-world experience with rapid ART initiation remains limited in resource-rich settings.DesignRetrospective cohort study.SettingA tertiary hospital in metropolitan Taipei, Taiwan.ParticipantsWe included 631 patients newly diagnosed as having HIV infection between March 2014 and July 2018.Main outcome measuresRapid ART initiation was defined as starting ART within 7 days after HIV diagnosis confirmation. HIV diagnosis, ART initiation and viral suppression dates and clinical outcome data were collected by reviewing medical records. The rates of loss to follow-up (LTFU), engagement in care and virological rebound at 12 months were compared between patients with rapid ART initiation and those with standard initiation.ResultsRapid ART initiation increased from 33.8% in 2014 to 68.3% in 2017, and the median interval between HIV diagnosis and viral suppression (HIV RNA load <200 copies/mL) decreased from 138 to 47 days. Patients with rapid ART initiation had a significantly higher rate of engagement in care at 12 months than did those with standard initiation (88.3% vs 79.0%; p=0.002). Patients aged <30 years had a higher risk of LTFU (HR: 2.19; 95% CI 1.20 to 3.98); and rapid ART initiation was associated with a lower risk of LTFU (HR: 0.41; 95% CI 0.24 to 0.83). Patients aged <30 years were more likely to acquire incident sexually transmitted infections (STIs) before achieving viral suppression.ConclusionsRapid ART initiation was associated with a higher rate of engagement in care at 12 months and shortened interval from diagnosis to HIV suppression. Delayed ART initiation may increase onwards HIV transmission considering the high rates of STIs.Ethics approvalThe study was approved by the Research Ethics Committee of National Taiwan University Hospital (Registration No. 201003112R).