Evidence for the hypertensive origin of Nigerian 'heart muscle disease' is presented. Epidemiologically, clinically and pathologically it is similar to hypertensive failure and it is associated with hypertension. It is more severe than hypertensive failure as judged by its prognosis and the myocardial damage at necropsy. The radiographic aortic width and renal histology, but not the retinal arteries have evidence of chronic hypertension in some. Using renal histology and scores on a discriminant analysis it was estimated that 34/62 cases in the necropsy series had been hypertensive . Up to 28 cases had not suffered from chronic hypertension but this figure (3%) of cardiac necropsies does not justify the identification of a highly prevalent myocardial disease in Nigeria. The arguments could apply to South African cryptogenic 'heart disease' and 'Jamaican cardiomyopathy'. The study presents data on the natural history of hypertensive failure.