This study examined the efficacy of one method for teaching diagnostic reasoning to occupational therapy students. During a clinical reasoning seminar in their first academic year, 80 entry-level occupational therapy master’s degree students in three successive classes were given three different levels of exposure to classroom-as-clinic or in-class evaluations of adults with physical or psychosocial disabilities. During the following summer, most students completed their first Level II fieldwork experience. Students’ grades for a second-year classroom-as-clinic experience with adults with physical disabilities were then compared across groups to determine the relative effect of the different seminar formats and fieldwork experiences. Students who had experienced in-class evaluations during their first academic year wrote significantly more accurate second-year evaluations than those who had not. Students who had completed psychosocial Level II fieldwork experiences were as accurate on their evaluations as students who had had physical dysfunction fieldwork experiences. The results suggest that in-class evaluations improve students’ diagnostic reasoning skills.