PURPOSE: To discuss the causes of treatment failure in percutaneous spine injections for low back pain or radiculopathy by analyzing patients who have experienced negative treatment effect on their first visit and a positive treatment effect on their second visit. MATERIALS AND METHODS: The authors reviewed the cases of 24 patients who visited the pain intervention outpatient department in our hospital due to back pain or radiculopathy. All patients reviewed experienced a negative treatment effect following their first spine injection, but a positive treatment effect following the second injection. The dates of the cases range from June 2003 to May 2004. Two radiologists analyzed the possible causes of the negative treatment effect following the first injection therapies by considering clinical aspects as well as reviewing radiological images. RESULTS: The most common condition was the presence of the change in the level of the second selective nerve root block (n=13). In seven cases, the methods for administering the injections were changed to facet block (n=2), midline epidural block (n=1), selective nerve root block (n=3) and caudal epidural block (n=1). In four cases, there were no changes in the methods for administering the injections nor were there any changes in the level of the selective nerve root block between first and second visit. In those cases, after reviewing spot radiographs performed during injection, we attributed the causes of failure of injection therapy to an inappropriate distribution of drugs. CONCLUSION: We can improve the effect of percutaneous spine injections for low back pain or radioculopathy by determining the exact level of perineural root block, trying alternative methods, and insuring a good distribution of the injected drugs.