OBJECTIVE:: We aimed to assess retention of HIV infected individuals in the Danish health care system over a 15-year period. METHODS:: Loss to follow-up (LTFU) was defined as 365 days without contact to the HIV care system. Data were obtained from the nationwide Danish HIV Cohort study, The Danish National Hospital Registry and The Danish Civil Registration System. Incidence rates (IR), risk factors for LTFU and return to care and mortality rate ratios (MRR) were estimated using Poisson regression analyses. RESULTS:: We included 4,745 HIV patients who were followed for 36,692 person-years. Patients were retained in care 95.0% of person-years under observation, increasing to 98.1% after initiation of antiretroviral treatment (HAART). The overall IR/100 person-years for first episode of LTFU was 2.6 (95% CI: 2.5-2.8) and was significantly lower after initiation of HAART (1.2 (95% CI: 1.0-1.3)). Five years after LTFU the probability of return to care was 0.87 (95% CI: 0.84-0.90). The risk of death was significantly increased after LTFU (MRR 1.9 (95% CI: 1.6-2.6)) and =6 months after return to care (MRR=10.9 (95% CI: 5.9-19.9)). CONCLUSIONS:: Retention in care of Danish HIV patients is high, especially after initiation of HAART. Absence from HIV care is associated with increased mortality. We conclude that high rates of retention can be achieved in a health care system with free access to treatment and is associated with a favorable outcome.