The retention curve for knowledge acquired in a consumer behavior course is explored in a longitudinal study, tracking individual students from 8 to 101 weeks following course completion. Rasch measurement is used to link tests and to achieve intervally scaled measures of knowledge. The findings indicate that most of the knowledge gained in the course is lost within 2 years. Evidence is provided that knowledge acquired at a deep level of understanding is more likely to be retained than knowledge acquired at a surface level of understanding, and knowledge tested more than once during a course is more likely to be retained than knowledge tested only once. No significant differences in retention were observed related to material covered in a project. Implications are discussed. (Contains 3 notes, 2 tables, and 1 figure.)