Six editions of Scholastic Aptitude Test-Mathematical (SAT-M) were factor analyzed using confirmatory and exploratory methods. Confirmatory factor analyses (using the LISREL VI program) were conducted on correlation matrices among item parcels--sums of scores on a small subset of items. Item parcels were constructed to yield correlation matrices amenable to linear factor analyses. The items constituting a parcel measured the same dimension, and parcels measuring the same construct were parallel to each other. Content area (arithmetic, algebra, geometry, and miscellaneous) defined the parcel. Confirmatory factor analyses of item parcel data indicated that the SAT-M editions were unidimensional across different ability populations. Full-information factor analysis (using TESTFACT) was also used to assess dimensionality within item parcels. Analyses assuming a two-parameter model and a three-parameter item response model suggested that all parcels were unidimensional. A third set of analyses involved least-squares factor analyses of a smoothed positive definite matrix of tetrachorics adjusted for guessing. Despite the corrections for guessing, difficulty factors emerged, suggesting that factor analysis of adjusted tetrachorics suffers from the same problems that have plagued other attempts to factor analyze item data. Results supported the unidimensionality of SAT-M, with no empirical justification for reporting subscores based on content. (GDC)