STUDY DESIGN: This is a prospective radiographic study. OBJECTIVES: We wanted to describe and quantify the common variations in the sagittal lumbar spine. SUMMARY OF THE LITERATURE REVIEW: No previous study of the spinopelvic parameters with a large cohort of asymptomatic young men was performed on subjects with the same ethnic background. MATERIALS AND METHODS: 166 young males without disease, trauma or a history of operation on the spine or lower extremities were included. The sagittal standing radiographs of the whole spine on 36 inch film were taken. The distances from the plumb line of C7, T12, the lumbar apex and the bicoxofemoral head to the posterosuperior corner of the sacrum were measured. Thoracic kyphosis, thoracolumbar kyphosis, lumbar lordosis, the segmental vertebral slopes, the sacral slope and the pelvic incidence were measured. Groups 1 and 2 were classified by having a sacral slope less than 35degrees (group 1: apex below L4, group 2: above L4). Group 3 had a sacral slope between 35degrees and 45degrees, and group 4 had a sacral slope greater than 45degrees. RESULTS: The average age was 21.8 years (range: 19~26 years). Group 1 contained 37 cases, group 2 had 44, group 3 had 62 and group 4 had 23. Thoracolumbar kyphosis was significantly increased in group 1 and lumbar lordosis and pelvic incidence were increased in groups 3 and 4. Thoracic kyphosis and the vertebral slope of T12 did not demonstrate any difference between the groups. CONCLUSION: The sagittal spinopelvic parameters showed significant changes according to the morphology of the lower lumbar spine. Understanding the patterns of variation in the spinopelvic parameters may help surgeons to plan treatment for various spinal lesions.