Abstract. Serum and urinary creatine and creatinine have been studied in eight patients with paralytic poliomyelitis. The serum and urinary creatine concentrations were strikingly high, while the corresponding creatinine concentrations were extremely low. The creatine/creatinine ratio showed an obvious change in both the serum and urine as compared to normal control values. The cause of the changes observed and their clinical implications are discussed.