This is a retrospective study that set out to determine the mortality patterns and case fatality rates of people with diabetes mellitus (DM) in a Nigerian hospital. The sources of data were the medical records, ward admissions, deaths register and death certificates. Of a total of 13,797 medical admissions made over a period of 11 years (1990-2000),1423 (10.3%) were DM related and the documented case fatality rate of DM was 22.6%.