The frequency and characteristics of definite lumbar scoliosis in an adult common low-back pain population (n = 671) were assessed by a clinical and radiologic prospective study. The prevalence was 7.5% (N = 50), increasing with age: 2% before 45 years; 15% after 60 years. Scoliosis was revealed by low-back pain in adulthood in 86% of the cases. The mean Cobb angle was 21 +/- 11.4 degrees. A Cobb angle of more than 30 degrees was noted in 16% of the scoliotics, thus 1% of the entire population. The proportion of women increased with the severity of the scoliosis. Right and left side scolioses were equally noted. A correlation between the Cobb angle and age was found (0.3 degrees/yr; P < 0.05). Rotatory olisthesis was noted in 34% of the cases, more often in right side curves (P < 0.01). The lumbar scoliotic patients were distinguished by a more advanced age (62 +/- 12.4 yr vs. 49.6 +/- 15.5 yr; P < 0.001), a greater proportion of women (72% vs. 48%; P < 0.01), and a more likely involvement of L3 and L4 radicular pain (P < 0.05). Radicular thigh pain was related to unstable curves (P < 0.01). The lumbar scoliotic patients thus constitute a subgroup within the low-back pain population.