The level of glomerular filtration rate can be estimated from the serum creatinine concentration and other easily measured patient variables from prediction equations developed using multivariable regression techniques. Recently, a new equation has been developed from the Modification of Diet in Renal Disease study, which is more accurate than other equations and more accurate than measurement of creatinine clearance. The authors recommend using prediction equations in clinical practice to estimate the level of glomerular filtration rate.