Background Data: Facet joint disorders are main source of chronic low back pain with a prevalence of 16.7%. Facet joint block is performed for diagnostic or therapeutic purposes and generally is carried out under computed tomography (CT) or fluoroscopy. Facet joint block is the gold standard in diagnosis of facet joint syndrome. It can also relief pain for up to 6 months. Purpose: To identify which imaging modality (CT or fluoroscopy) is more suitable to guide the procedure of lumbar facet joint block, and results in better relieve of symptoms. Study Design: Prospective analytic clinical case study. Patients and Methods: Sixty eight lumbar facet joints representing 24 patients were injected in the radiology department, Suez Canal University Hospital, Ismailia, Egypt from 1/2005 to 12/2010. All cases were suspected of having facet joint disorders based on clinical and radiological data. After clinical examination and reviewing lumbar images to identify target facets, every patient underwent facet joint block under either CT or fluoroscopy. Visual Analogue Scale was used to assess improvement of symptoms. Results: Fluoroscopy was more successful in guiding the injections (success rate 77.7% compared with 31.25% in CT guidance). It is also faster (6:37 minutes per joint compared with 10:54 minutes for CT guidance). Less number of trials were required (1.7 trial compared with 6.6 trials with CT guidance). Fluoroscopy exposed the patients and the radiologist to much irradiation (21.3 rad compared to 0.3 rad in CT guidance). Decreased bone density and laminectomy impair fluoroscopy guidance. CT guidance is difficult in patient with marked arthropathy and coronally oriented joints (8 trials compared with 5.6 for normally appearing joints). Both groups showed significant improvement of symptoms. Conclusion: Fluoroscopy should be the primary choice for guiding lumbar facet joint block. It is more successful and faster. Its disadvantages include much irradiation to patients and radiologists, and difficulty in patients with laminectomy and decreased bone density. CT can then be used to guide the block. Both techniques are effective in pain reduction. (2012ESJ035)