Pain descriptors of patients with low back pain were analyzed to determine their usefulness in identifying patients without demonstrable organic disease. Using a standardized back pain questionnaire which scales qualities of pain along 7 independent factors, it was possible to make clear distinctions between the subjective reports of patients with and without demonstrable organic disease of the lower back. Pain described by patients with demonstrable organic disease tends to be consistent and specific; whereas pain described by patients without demonstrable organic disease tends to be more variable and diffuse. Pain reported by the latter group was also more intense. Factors which may underlie these findings were discussed.