A total of 6,321 school children were screened using Moiré topography in Ottawa in 1979. Analyses of 400 roentgenograms showed that 39% had rotation of a nonstandard variety. The most common type was rotation extending beyond the end vertebra by more than one level. Seven percent had rotation to the opposite side of the major curve; 4% showed asymmetry due to isolated vertebral rotation without any lateral curve. The correlation of the Moiré hump to the area of the lateral curve and vertebral rotation is recorded.