Selective spinal nerve block is a useful tool in today's multidisciplinary approach to the diagnosis and treatment of low back pain. The indications, sources of spinal pain, block technique, result interpretation, complications and clinical applications relevant to the subject are discussed. The value of a spinal nerve block relies on an understanding of the pain elements in the back, nerve innervations and careful patient selection. If the technique is performed properly and the results are interpreted cautiously, selective spinal nerve block may prove helpful, especially for patients from whom diagnostic information is inadequate. In some cases, therapeutic effect including that from surgical intervention can be achieved selectively at the symptomatic root. However, controversy remains and therefore well designed clinical studies are needed to provide more information about the validity of this diagnostic and therapeutic modality.