[en] The total plasma (E₁) and renal plasma (E₂) clearances of [⁵¹Cr]EDTA were measured simultaneously in 40 patients with a wide range of renal function. The regression equation was E₁ = 0.997E₂ + 4.1; the slope of the regression line was not significantly different from 1.00, and the intercept differed significantly from zero. The results suggest that [⁵¹Cr]EDTA has a significant extrarenal clearance of approximately 4 ml/min, independent of renal function. The data are used to correct the total [⁵¹Cr]EDTA plasma clearance, measured by a simplified method, to yield a rapid, accurate and precise measurement of glomerular filtration rate for routine clinical use. (Auth.)