A case-series study of all admissions using patient registers was carried out to analyse patterns of medical admissions into the Medical Intensive Care Unit (MICU) of the Addis Ababa University Teaching Hospital, and evaluate for any changes in that pattern over a study period. All patients admitted to the MICU of a 500-bed Teaching Hospital in Addis Ababa between 1985-2000 were the study subjects. Demographic variables, specific categories of diagnoses and their outcomes were recorded A total of 3548 patients (male to female ratio of 1.4:1, mean age 37.10 +/- 17.29) were admitted from September 1985 to August 2000. Acute infectious and cardiovascular diseases accounted for half of the entire critical care admissions with infectious diseases accounting for 30%. Among specific diagnoses, diabetic ketoacidosis was the leading cause of admission followed by acute myocardial infarction and severe and complicated malaria, each accounting for 10.7, 9.8 and 9.3% of all admissions respectively. Trends of admissions over the sixteen-year period showed steady increase in relative frequency of acute complications of non-communicable diseases consisting of diabetes, acute myocardial infarction and stroke while infectious diseases showed interspersed peaks of admissions coinciding with epidemics. The overall mortality of the MICU was 32%, with proportionally more female deaths, 34.8 versus 29% (P = 0.0002). Severe and complicated malaria was the leading cause of death (10.3%) followed by tetanus (6.4%) and acute myocardial infarction (6.3%). The increase in relative and absolute frequency of acute complications of non-communicable diseases most probably heralds an emerging epidemic of non-communicable diseases related to life style changes in the urban well to do in addition to existing problems of infectious diseases of poverty.