The aim of this study was to evaluate the usefulness of M-mode echocardiography as a non-invasive diagnostic tool when facilities for cardiac catheterization were not available. We used this technique to study 275 patients whose clinical diagnosis included hypertension, rheumatic heart disease, cardiomyopathy, peripartum cardiac failure, pericardial disease and some forms of congenital heart disease. Characteristic echocardiographic patterns made specific cardiac diagnoses possible and allowed a distinction to be made between clinically similar conditions. It is concluded that echocardiography is very useful in the African setting because it is safe and repeatable.