Students with differing profiles of epistemological beliefs--their beliefs about personal epistemology, intelligence, and learning--vary in thinking, reasoning, motivation, and use of strategies while working on academic tasks, each of which affect learning. This study examined students' epistemological beliefs according to gender, school orientation, overall academic achievement, and performance on two differently structured academic tasks. Epistemological beliefs in fixed and quick ability to learn, simple knowledge, and certain knowledge differed significantly as a function of gender, school orientation, and levels of academic achievement. These beliefs, particularly the belief in simple knowledge, significantly predicted overall performance and reflective judgment scores on the ill-structured task but not on the well-structured task. Implications concerning the relations among epistemological beliefs, reflective judgment, gender, school orientation, task structure, and achievement are discussed. (Contains 3 tables and 1 figure.)