Objective:To investigate whether the activity of 5' -nucleotide phosphodiesterase (5'-NPD) in urine of rats could be used as a marker for monitoring the early dam age of kidney induce by cisplatin (DDP) Methods:T he rats model of kidney-damage induce by DDP was established After the rats were treated with DDP, the change s of 5'-NPD activity in urine samples were measured and the histopathologic chan ges of kidney were observed under light and electric microscopes to decide firmly the relationship between 5'-NPD activity and the early damage of kidney induce by DDP Results:The rats were randomly divided into high dose DD P group,low dose DDP and control group The activity of 5'-NPD in urine and the histopathol ogic changes of the kidney were not significantly different between low dose DDP group and control group in the experiment The activity of 5'-NPD in urine incr eased on the second day after high dose DDP administration and the highest level was found on the 4th day It's higher than that of the group of control and low dose DDP The histopathologic changes of kidney occurred later Moderate dilati on in renal tubules and inflammatory cell infiltration was found in some areas of rat's kidney on the 8th day The necrosis occurred in many renal parenchyma cellson the 15th day Conclusion:The level of 5'-NPD in urine sample can reflect sensitively the damage of kidney induced by DDP and can be u sed as a maker for monitoring the early damage of kidney induced by DDP