For reasons of convenience, the extent of 24-hour proteinuria was increasingly abandoned by nephrologists in favor of urinary protein/creatinine ratio (UPCR). The use of UPCR measured on a sample of urine overcomes the inaccuracies related to the collection of 24 or variations in urine concentration. This report has been validated against the 24-hour proteinuria for screening or monitoring of renal glomerular diseases by the French Society of Nephrology. In theory, the UPCR is measured on a urine sample, taken preferably in the morning. In practice, the precision of a measurement at any time of day is quite acceptable.