Item responses of two samples each of 622 normal and 573 educable mentally retarded children, 6 to 15 years of age, on Raven's Colored Progressive Matrices were submitted to a principal components analysis and varimax rotation. The following four factors were obtained: continuity and reconstruction of simple and complex structures, discrete pattern completion, reasoning by analogy, and simple continuous pattern completion. The factors corresponded to readily identifiable problem types. Comparability of factor structures of normal and retarded subjects indicated the factorial invariance of the test with children of different IQ levels. (Author)