A substantially revised Medical College Admission Test (MCAT) was introduced in spring 1991. The new examination is designed to assess critical thinking skills, basic concepts and problem solving facility in science, and writing skills. This paper reports preliminary findings on the factor structure of the revised MCAT, which consists of four sections: Verbal Reasoning, Physical Sciences, Writing Sample, and Biological Sciences. It was found that a four-factor solution was appropriate for three samples (6,776 students, 1,699 students, and 2,336 students, respectively) selected from three forms (Forms 952, 773, and 105, respectively) administered in spring 1991. A verbal reasoning factor and a writing factor were clearly defined in all analyses. A physics/chemistry factor and a biology factor were found for the total group, White group, and males. A general science factor was found for females, Asians, and Blacks. Factor correlations were compared to correlations between approximately comparable reported scores, and patterns were consistent. Results suggest that the verbal reasoning and writing sample sections have the anticipated internal structures. Because organic chemistry variables load with variables from the physical sciences section rather than the biological sciences section, science variables bear further examination. Additional research on the construct validity of the MCAT is planned. Seven tables present study data. (Author/SLD)