Limited data exist on the impact of dementia in developing nations, including its association with mortality. The purpose of this paper is to assess the relationship between dementia and five-year mortality on a community dwelling elderly Yoruba population in the developing country of Nigeria and to compare those results with those from an elderly African-American community in Indianapolis. A two-phase design was used to ascertain dementia status in two sites. In the first phase, the Community Screening Instrument for Dementia (CSI-D) was administered. In the second phase, subjects were sampled for the clinical assessment according to their CSI-D performance category. Proportional hazards regression was used to assess the relationship between mortality and cognitive status at both sites after adjusting for demographics and chronic disease conditions. For the entire screened population, poor and intermediate performance on the CSI-D is associated with increased mortality at both sites; however the effect of CSI-D performance did not significantly differ between the two sites. For the clinically assessed sample, dementia was significantly associated with increased mortality at both sites (Ibadan RR = 2.83, Indianapolis RR = 2.05), but the effect was not significantly different across the two sites. Dementia resulted in an increased risk of mortality for Yoruba of a magnitude similar to African-Americans suggesting that the impact of dementia on mortality risk may be similar for developing and developed countries. Copyright 2002 John Wiley & Sons, Ltd.