The urinary elimination of creatinine (60275) and its use as a means to express urine concentrations were reviewed and discussed. A description of renal elimination was presented, and the urinary elimination of creatinine was reviewed. The analytical determination of creatinine in urine using a modified Jaffe reaction was described. Studies have demonstrated good precision using this technique on replicate samples and on procedures performed on different days; however, other studies have shown large differences in the accuracy of results obtained in different laboratories. Factors that have been found to influence the urinary elimination of creatinine include diurnal variations, body mass, age, sex, health status, diet, diuresis, exercise, drug use, alcohol use, tobacco use, and incomplete voiding of the urinary bladder. Limitations in the use of creatinine values to correct urine samples were discussed. Other procedures that can be used to correct urine samples such as body size and mathematical corrections were described.