A series of 190 patients with lumbar spondylolisthesis treated operatively during the years 1948-80 at the mean age of 15.2 years (8-19 years) and reexamined 4-36 years (mean 11.2 years) later are presented. In 92 of them (48%) scoliosis (more than 5 degrees) in association with olisthesis was seen. The slipping affected the fifth segment in 90 and fourth segment in two patients. The female predominance was characteristic in the scoliotic group. Dysplastic changes of the posterior arc were more often seen in the group of patients with scoliosis than in the nonscoliotic group, and they also presented a more severe grade of slipping and lumbosacral kyphosis. The curve was usually mild and was situated in the lumbar area. Patients with a higher degree of lumbosacral kyphosis and more severe slipping also had a statistically higher degree of lumbar scoliosis. Operative treatment of spondylolisthesis consisted of posterior or posterolateral fusion in situ, but two patients were treated using ventral fusion and three severe cases with removal of loose posterior element. Lumbar scoliosis classified as sciatic type disappeared in 25 out of 39 patients after lumbosacral fusion, suggesting the "sciatic muscle spasm" as an etiologic factor. The torsional type of curve resulting from asymmetrical slipping of the vertebra was also corrected in 19 out of 28 cases after fusion. At follow-up patients with remaining lumbar scoliosis represented more low-back pain than those without any curve. In our opinion lumbosacral fusion is indicated before lumbar curve changes to structural scoliosis in symptomatic patients.(ABSTRACT TRUNCATED AT 250 WORDS)