Facet (zygapophysial) joint pain can be diagnosed by anesthetization of the medial branch divisions of the dorsal rami. In accordance with the criteria established by the International Association for the Study of Pain, lumbar facet (zygapophysial) joints have been implicated as the source of chronic pain in 15% to 45% of the patients with chronic low back pain. The reasons for the wide variations have not been systematically evaluated. This study was designed to determine the prevalence of facet (zygapophysial) joint pain in patients suffering with only low back pain and compare this prevalence to the prevalence in patients with painful involvement of multiple regions of the spine. A total of 300 patients in an interventional pain management setting, presenting and undergoing diagnostic interventional procedures consecutively, either with involvement of a single region (low back only) or multiple spinal regions (low back pain and neck pain or thoracic pain) were evaluated. There were 150 patients in each group. All patients were treated with diagnostic medial branch blocks with 1% lidocaine to test the presence of facet joint pain. Lidocaine-positive patients underwent a subsequent confirmatory block with 0.25% bupivacaine. Medial branches were blocked at two levels to block a single joint. Prevalence of lumbar facet joint pain in patients with low back only was 21%, compared to 41% of the patients with low back pain with involvement of other regions of the spine with controlled comparative local anesthetic blocks. A false-positive rate of 17% in patients with low back pain only and 21% in patients with involvement of multiple regions of the spine was demonstrated with single blocks. This study demonstrated a lower incidence of facet joint pain in patients with spinal pain of a single region in the low back compared to the patients with multiple region involvement of the spine (21% vs 41%), in an interventional pain management setting. These results may not be extrapolated to the general population or chronic low back pain population at large.