Study Design : This study is a prospective evaluation of the effect of several operative positions on lumbar sagittal alignment by radiographic analysis of 20 healthy volunteers. Objective : The purpose of the study was to compare operative tables commonly used for spinal procedures and to determine which positions reproduce normal lumbar lordosis. Material and Methods : Healthy twenty volunteers aged 20-35 years were enrolled in the study. No subject had a history of low back pain and lumbar surgery. Each volunteer underwent a lateral radiographs with tube to film distance 1m and beam centered on L3 vertebra. Five radiographs were taken for each volunteer, in standing, prone position on OSI table with 0 hip flexion,90 hip flexion, 60 hip flexion and prone position on four poster frame with 0 hip flexion. Intervertebral segmental angel from Ll to S1, lordotic angle from Ll to L5 and Ll to S1 were measured using a goniometer with 1 precision. To check intra and inter-observer error of radiogaphy measurements, repeated measurements of radiography by one personnel and three different personnel were done and coefficient of variation was below 5%. Data was analyzed with SPSS and ANOVA was used for a statistical comparison. Results : All segmental and lumbar lordotic angles showed no statistically significant difference between standing and prone position on four poster frame. All segmental angles, except Ll -2 and L2-3 segments, showed no difference between standing and prone position on OSI table with 0 hip flexion. Segmental and lumbar lordotic angles of prone position with 90 hip flexion and 60 hip flexion revealed statistically significant difference from standing position. Conclusion : Physiologic lordosis values were produced only by the prone position on the four poster frame and prone position on OSI table with 0 hip flexion. Prone positions with 60 and 90 hip flexion resulted in statistically significant decrease in lumbar lordosis.