This study was undertaken to examine the removal rate of guanidino compounds (GS) as uremic toxin in the small animal models of acute renal failure (ARF) undergoing hemodialysis. For this purpose, the methodological trial of hemodialysis was done to determine the clearance and removal rate of solutes, ultrafiltration rate and pressure in vitro, and extracorporeal blood flow in vivo. The mean removal rate of methylguanidine (MG) and guanidinosuccinic acid (GSA) was 33.8% and 56.0% respectively. Correlation was only observed between GSA and creatinine, GSA and arginine. But MG was not correlated with other GC. These results indicate that MG and GSA are important indicators to start hemodialysis and to understand metabolic disorder in ARF.