The measurement of vertebral rotation according to Perdriolle is widely used in the French-speaking and Anglo-American countries. Even in this measurement technique there may be a relatively high estimation error because of the not very accurate grading in steps of five degrees. The measurement according to Raimondi seems to be easier to use and shows a better accuracy with two-degree steps. The purpose of our study was to determine the effectivity of both common measuring methods. The apex vertebra of 40 curves on 20 ap-radiographs were measured by using the Perdriolle torsionmeter and the Regolo Raimondi. Interrater and intrarater reliability were computed. The thoracic Cobb angle was 43 degrees , the lumbar Cobb angle 36 degrees. The average rotation according to Perdriolle was 19.1 degrees thoracic (SD=11.14), lumbar 12.7 degrees (SD=11.21). Measurement of vertebral rotation according to Raimondi showed an average rotation of 20.25 degrees in the thoracic region (SD=11.40) and lumbar of 13.4 degrees (SD=10.92). The intrarater reliability was r=.991 (Perdriolle) and r=.997 (Raimondi). The average intrarater error was 1.025 degrees in the Perdriolle measurement and 0.4 degrees in the Raimondi measurement. Interrater error was at average 3.112 degrees for the Perdriolle measurement and 3.630 degrees for the Raimondi measurement. This shows, that both methods are useful tools for the measurement of vertebral rotation for the experienced clinician. The Raimondi ruler is easier to use and shows a slightly better reliability.