Within a 10 years period, 612 patients underwent an autopsy, in a geriatric hospital. Seventeen p. 100 were discovered to have a high blood pressure. Twenty-nine patients (that is about 4 p. 100) presented with a small unilateral kidney. The pathogenetic factors of these unilateral nephropathies were various, many causes of which were unilateral pielonephritis. Out of the patients exhibiting a small unilateral kidney, 62 p. 100 had a high blood pressure. Hypertension due to a unilateral nephropathy, when studied on a statistic level, does not induce any atheromatous lesion nor heart ponderal hypertrophy more acute than essential high blood pressure. The unilateral nephropathies hypertension would thus be compared to an hypertension "depending on sodium or volume" and not as an hypertension "depending on renin".