Rats with experimental renal hypertension were fed various diets differing in sodium and protein content. Marked prolongation of life was achieved by rice diet. Polyarteritis nodosa developed, as a result of the experimental procedures, in 23.5 per cent of the animals. Its incidence was closely correlated to sodium ingestion: 4 per cent in rats on low sodium intake, 36 per cent in rats on normal or slightly higher sodium intake. Protein intake showed no effect on incidence of polyarteritis but distinct effect on survival time. Except for one rat where a sarcoma destroyed almost all kidney tissue, no animal on rice diet developed polyarteritis nodosa.