This study evaluated brief, in-class write-to-learn assignments as a tool for promoting learning and retention in large, introductory psychology courses. A within-subjects (student) design was used with assignment of concepts to write-to-learn and copy (control) conditions counterbalanced across sections for each instructor. Students performed better on exam questions that pertained to concepts they actively wrote about than those that pertained to conceptual information they copied from an instructor's slide. On a retention test taken approximately 8.5 weeks after the course, students continued to perform better on write-to-learn concepts than on copied concepts. The findings suggest that write-to-learn assignments facilitate active processing of lecture material, which produces modest benefits for learning and retention of key, conceptual knowledge.