Loss to follow-up (LTFU) of clients from antiretroviral therapy (ART) has a great negative impact on the immunological benefits of ART, and increased acquired immune deficiency syndrome related morbidity and mortality. The purpose of this study was to analyze socio-demographic characteristics related to LTFU among HIV and AIDS patients in Semarang City. A case-control study was carried out at Hospitals and Primary Health Centre. Patients who did not take anti-retroviral for 3 months were defined as LTFU while those regularly take anti retro viral for 3 months became the controls. The total sample of the research were 134 respondents obtained by purposive sampling technique. Chi square and logistic regression tests were performed to analyze factors associated with LTFU. The multivariate analyses showed the most dominant factors that influence with LTFU was education level (OR = 6.27. 95% CI: 2.29, 17.09). Intervention on literacy program should be emphasized to patients who are about to start and during the ART program.