The herniated nucleus pulposus (HNP) is a very common disorder. In those patient who do not respond more direct therapeutic measures may be necessary The chymopapain cheomonuclelysis after two decades of development has provided a variable alternative to surgical diskectomy for treatment of HNP. The changes of CT scan follow-up 1 month and 3 month that occur in the disks of those patient who res-pond to chymopapain chemonucleolysis must be defined and evaluation of thmporal radiographic changes may also help clarity mechanism by which chemonucleolysis relieves sciatic pain caused by HNP. The results were as follows; 1. Our data indicates that chymopapain chemonucleolysis was effective in 70% and 90% of patients at both 1 M and 3M follow-up(average 80%) 2. At 1 M. follow-up a successful response was noted in 70% and 90% of pa-tients with 70% of them showing significant narrowing(average 1.2mm) and ovservable diminution inthe herniated disc fragment (average 1.5mm) The refor with 3 M follow-up the CT changes did become more pronounced with greater number of patients exhibiting a diminution of the disk herniation and interspace narrowing and associated with more progressive improvement of clinical outcome. 3. New vacuum phenomenon and extradiskal effects of chymopapain apperar to be absent, 4. At 1 M follow-up Housefield Unit(HU) of disk is generally increased (average 8.8 HU) and at 3 M. follow-up it is decreased (average 6 HU).