The purpose of this research was to investigate hypothesized relations of visuospatial and logical reasoning skills, and span of short-term memory to achievement in geometry. In addition, major subfactors of visuospatial ability (visualization, speeded rotations, spatial orientation, and disembedding) were assessed to determine which were significant predictors of geometry achievement. Vernon's (1965) model of intelligence and Baddeley's model of working memory provided the theoretical framework for these hypotheses. Subjects (N = 110) were students in seven sophomore level geometry classes in two schools in southwest Virginia. Cognitive measures of speeded rotations, visualization, spatial orientation, disembedding, Gestalt closure, logical reasoning, and short-term memory span were administered. Two measures of geometry achievement were used: The standardized New York Regents Geometry Exam, and z-transformations of the classroom final grade. A model of geometry achievement is proposed and major predictions of the model were supported. within this sample, regression analysis showed the measures of visualization, logical reasoning, and short-term memory predicted achievement on the New York Regents Geometry Exam. Separate regression analyses for each gender revealed visualization predicted geometry achievement for the girls, while logical reasoning and short-term memory span predicted geometry achievement for the boys. Gender differences favoring boys were found on measures of speeded rotations, spatial orientation, and Gestalt closure. Girls had significantly higher scores on the measure of short-term memory span and the classroom measure of geometry achievement. / Master of Science