The diagnosis of pyelonephritis, especially primary one, is very difficult because its complicated clinical manifestations. In our previous paper, a description was made concerning the diagnosis of pyelonephritis by means of urological X-ray examinations. This article deals with the effect of administration of adrena l steroids on the excretion of organisms in the separated renal urine in patients with and without pyelonephritis and other renal disorders. The num b er of organism in the separated renal urine did not show a significant change in normal subjects, but a considerable increase in excretion of organisms was demonstrated in patients with chronic and acute pyelonephritis. However there was no difference between chronic and aute pyelonephritis. Histological studies were performed on surgically removed kidneys in a few instances. The side-effects of adrenal steroids were thought to be negligible. It is concluded that the provocative test described here is very useful for di a gnosis of pyelonephritis.