Several reports have described the application of conventional item-analysis procedures to the Wechsler subtests (6, 7, 9, 12, 13). That these results have not been completely consistent has readily been attributed to differences in the samples studied by different investigators. It may be noted, however, that if the items of a particular subtest really do all measure the same thing then no amount of difference in the sampling of people can bring about a significant change in the apparent order of difficulty of the items. Where such changes in the order of difficulty have been observed it is clear that the items must depend reliably on more than one dimension of performance, at least on two dimensions and possibly on as many dimensions as there are items. In particular, the multidimensional character of the Picture Completion (PC) subtest has recently been explicitly demonstrated ( 16), with the isolation of three common factors from the 20 items that were studied. At the same time, evidence was adduced showing that these three factors could be interpreted in terms of clinically distinct processes, and that they were differentially related to certain of the subtests other than PC. Given such encouragement, it appears pertinent to investigate the factorial composition of at least some of the remaining Wechsler subtests, in order to provide a better understanding of what is measured by the scores currently being obtained (21) by adding together item responses of heterogeneous content. The present report is concerned primarily with the Information (I) and Arithmetic (A) subtests of the WAIS.3 We chose to treat more than one of the subtests at a time, where possible, in order to reduce the number of factor analyses required to cover all the subtests. We chose to treat I and A together, *This research was supported by the Society for the Investigation of Human Ecology. This report may be regarded as the fourth in a series ( 15, 16, 18) concerned with the general question of relationships between aptitude and achievement tests, on the one hand, and various measures of personality on the other. The Wechsler provides a useful starting point for studies in this area since it appears to span a number of representative ability dimensions, and is widely employed clinically in the understanding of personality disorders. This report contributes to the overall series by providing additional information about six of the dimensions measured by the Wechsler. 31t has been suggested that marker should be included if a study such as this is to succeed in finding out what the WAIS really measures. There are three reasons why we have not adopted such a strategy at this stage of our investigation. (a) The necessary data are not currently available to us, and would be relatively difficult to obtain. (b) In terms of common factors, tests cannot possibly exhibit a better simple structure than items. (c) From the viewpoint of those whose experience is with the Wechsler, individual items may serve as even more meaningful markers than any collection of less familiar factor-pure tests.