BACKGROUND: Prior to the scale-up of antiretroviral therapy (ART), demographic surveillance cohort studies showed higher mortality among migrants than residents in many rural areas. OBJECTIVES: This study quantifies the overall and AIDS-specific mortality between migrants and residents prior to ART, during ART scale-up, and after widespread availability of ART in Rufiji district in Tanzania. DESIGN: In Health and Demographic Surveillance System (HDSS), the follow-up of individuals aged 15-59 years was categorized into three periods: before ART (1998-2003), during ART scale-up (2004-2007), and after widespread availability of ART (2008-2011). Residents were those who never migrated within and beyond HDSS, internal migrants were those who moved within the HDSS, and external migrants were those who moved into the HDSS from outside. Mortality rates were estimated from deaths and person-years of observations calculated in each time period. Hazard ratios were estimated to compare mortality between migrants and residents. AIDS deaths were identified from verbal autopsy, and the odds ratio of dying from AIDS between migrants and residents was estimated using the multivariate logistic regression model. RESULTS: Internal and external migrants experienced higher overall mortality than residents before the introduction of ART. After widespread availability of ART overall mortality were similar for internal and external migrants. These overall mortality experiences observed were similar for males and females. In the multivariate logistic regression model, adjusting for age, sex, education, and social economic status, internal migrants had similar likelihood of dying from AIDS as residents (adjusted odds ratio [AOR]=1.14, 95% confidence interval [CI]: 0.70-1.87) while external migrants were 70% more likely to die from AIDS compared to residents prior to the introduction of ART (AOR=1.70, 95% CI: 1.06-2.73). After widespread availability of ART with the same adjustment factors, the odds of dying from AIDS were similar for internal migrants and residents (AOR=1.56, 95% CI: 0.80-3.04) and external migrants and residents (AOR=1.42, 95% CI: 0.76-2.66). CONCLUSIONS: Availability of ART has reduced the number of HIV-infected migrants who would otherwise return home to die. This has reduced the burden on rural communities who had cared for the return external migrants.