Clinically, the commonly used routine test for assessing impaired renal function is the determination of creatinine clearance. The traditional 24 hour urine collection method is unreliable and inconvenient, particularly in ambulatory patients and outpatients because of errors in collection, timing of collection, and measurement of urine volume. The purpose of this study was to evaluate the possibility of determining creatinine clearance from urine collected for less than the traditional 24 hours. Thirty clinically healthy adult subjects with no history of renal dysfunction were used for the study. Each of the subjects had his creatinine clearance determined from 4 hour, 20 hour and 24 hour urine collections as well as from the formula of Cockcroft and Gault. The mean creatinine clearance obtained from 4 hour urine collection (male = 92.8 ml/ min/1.73 m2 & female = 84.5 ml/min/1.73 m2) and 20 hour urine collection (male = 98.9 ml/min/1.73 m2 & female = 88.6 ml/min/1.73 m2) shows no significant difference from that obtained from the traditional 24 hour urine collection (male = 97.9 ml/min/1.73 m2 & female = 88.1 ml/min/1.73 m2) (P > 0.05). We therefore suggest that determination of creatinine clearance from fewer hours of urine collection especially in patients with renal impairment be explored towards their adaptation to routine practice.