Sex differences on Perry's stages of epistemological development were investigated in a study of 100 freshmen (50 men and 50 women) at a large midwestern university. A semi-structured interview probed six domains related to Perry's theory, including the role of the learner, instructor, and peers in the learning situation, the question of evaluation of learning, the nature of knowledge, and educational decision making. Students also completed the Measure of Epistemological Reflection (MER), based on Perry's first five levels, and the Learning Style Inventory (Kolb). No significant differences emerged in either MER or interview means by sex. But there was evidence of gender-related (though not gender-specific) patterns in the use of certain reasoning structures. At Position Two, where knowledge is seen as certain, females expressed hesitancy to speak in class or criticize authority. They emphasized peer-support connections in receiving knowledge. Males described an active, critical search for answers and engaged peers in argument and quizzing. At Position Three, where awareness of some uncertainty begins, females tend to adopt a subjective knowledge stance, whereas males prefer working through uncertainty with logic and debate. Data from the Learning Style Inventory was inconclusive. Educational implications are considered. (LPG)