Which undergraduate degree programs at the University of Colorado at Â鶹¹ÙÍø enroll the most students? The answers might surprise you. The largest department at CU, based on spring figures, is psychology by a long-shot. Almost twice as many students study psychology - 1,446 - as the No. 2 major, communication. However, if the number of students in both the molecular (733) and environmental (719) biology departments are combined, biology gets the top spot at 1,452.