A cohort of 321 men between the ages of eighteen and fifty-five was randomly selected from a group of 1221 men who had been surveyed by a questionnaire. They then had radiographs made of the lumbar spine. Of the 292 subjects fulfilling the criteria for inclusion in the study, ninety-six (32.9 per cent) had never had low-back pain, 134 (45.9 per cent) had had or were having moderate low-back pain, and sixty-two (21.2 per cent) had had or were having severe low-back pain. In the three groups there was a similar frequency of transitional vertebrae, Schmorl's nodes, the disc vacuum sign, narrowing of the disc space between the third and fourth lumbar and the fifth lumbar and first sacral vertebrae, and claw spurs. When there were traction spurs or disc-space narrowing, or both, between the fourth and fifth lumbar vertebrae, an increased incidence of severe low-back pain was evident. There also was a significant association of these two radiographic findings with symptoms (pain, weakness, and numbness) in the lower limbs. The measured lumbar lordosis, the length of the transverse process of the fourth lumbar vertebra, and the relationship between the fourth and fifth lumbar vertebral bodies with reference to the intercristal line had no association with the low-back pain. Increased lumbar lordosis had a significant association with decreased disc-space height and wedging deformity of the disc between the fourth and fifth lumbar vertebrae.(ABSTRACT TRUNCATED AT 250 WORDS)