We compared relationship among three single blood sampling methods which have been proposed for determination of plasma clearance with 99mTc-MAG3. Russell's and Bubeck's algorithms were employed for 48 adults (average age: 53 years) and Bubeck's and Piepsz's algorithms were used in 9 children (average age: 5.8 years). Three methods showed very high correlation among them. However, Russell's and Piepsz's methods were about 1.4 times higher than Bubeck's method in calculating plasma clearance of 99mTc-MAG3. The present study indicates that three methods discussed here are useful for the determination of plasma clearance with 99mTc-MAG3. In addition, Bubeck's method may be preferable as a reference for single plasma sampling method because of common application to adults and children.