This paper described one part of an item response theory (IRT) feasibility study performed for the Aptitude Test portion of the Graduate Record Examinations (GRE). The dimensionality of the GRE verbal and analytical sections is discussed. The results of six different types of equating of the verbal section and four different types of equating of the analytical section for one form of the test, A, are compared to those of another form of the test, B. Although the absolute robustness of the various types of equating to violations of the assumption of unidimensionality cannot be determined by this research, information about the relative robustness is provided. Two forms of the GRE Aptitude Test were administered in June 1980. For Form A, the IRT analyses were based on a sample of about 3,000 examinees, while linear and equipercentile equatings were based on a sample of about 9,000 examinees. For Form B, the analyses were based on approximately 5,000 and 15,000 examinees, respectively, for IRT and non-IRT analyses. The study results are inconclusive. Simulation studies are recommended to shed light on the effects of multidimensionality on equating. Two data tables and four graphs conclude the document. (TJH)