One hundred seventy-six consecutive patients with chronic low-back pain and no history of previous lumbar surgery were studied to test the clinical criteria of Fairbank et al. and Helbig and Lee for zygapophysial joint pain. All patients underwent a history, examination, and a series of zygapophysial joint injections or blocks of the medial branches of the dorsal ramus with lignocaine. Those patients responding to the first series of blocks were given confirmatory blocks using bupivacaine. None of the clinical features tested was found to be associated with response to the confirmatory block. The Fairbank et al. and Helbig and Lee criteria were shown to be unreliable in distinguishing pain of zygapophysial joint origin from pain of other origins.