Objective: Mild cognitive impairment (MCI) is recognized as a high-risk condition for conversion to dementia, although data on outcomes of MCI in sub-Saharan Africa are scarce. We investigated outcomes of MCI over a 4-year period in Tanzania and considered risk factors for conversion to dementia. Methods: In a longitudinal cohort study in the Hai district, Tanzania, patients with MCI were identified during a two-phase prevalence study carried out in 2010. Of 1,198 people aged 70 years and over screened in phase I, a stratified sample of 296 were fully assessed in phase II. MCI was defined according to international consensus criteria. DSM-IV criteria were used for dementia diagnosis. Background demographic and risk factor data were collected, and neuropsychiatric symptoms were assessed using the neuropsychiatric inventory. Patients were followed-up in 2011, 2012 and 2014. Results: Forty-six MCI patients were identified. After adjusting for stratification, the crude prevalence of MCI was 7.0% (95% CI: 3.6e10.4). Over a 4-year period, 15 patients (32.6%) progressed to dementia, 2 patients (4.3%) returned to normal cognition, 1 developed late-onset schizophrenia, 8 patients (17.4%) had stable MCI, 19 patients (41.3%) died, and 1 refused assessment. Age, sex, education levels, body mass index, hypertension, and comorbidity were not associated with progression to dementia. Conclusion: In this rural Tanzanian population, rates of conversion from MCI to DSM-IV dementia were similar to those reported in high-income countries. Over a third of all patients had died at the 4-year follow-up