We evaluated the formulas of urine-free prediction of creatinine clearance (CCr) for clinical use in the patients with chronic glomerulonephritis (CGN). Subjects were 246 patients with CGN diagnosed by renal biopsy with range from normal renal function to end stage renal failure. CCr were measured exactly with urine collections more than 2 times and compared with the values calculated using four urine-free mathematical formulas of Cockcroft et al, Mawer et al, Konishi et al, and Tozune et al. Strong, statistically significant correlations were observed between CCr estimated with each prediction method and measured CCr (r > or = 0.946). However, the latter two formulas tended to overestimate the values. Predicted errors more than 20% of the formula of Cockcroft et al, were the least. And their formula was the easiest for clinical use because of the simplicity for learning by heart. We conclude that these four formulas can be used with reasonable accuracy in the patients with CGN from normal renal function to end stage renal failure, and the formula of Cockcroft et al, is the most recommendable for clinical use.