We report results on an experiment to promote conceptual change in the introductory calculus-based mechanics course using an approach based on collaborative learning. The approach is based on the notion of conceptual conflict developed by Hewson and Hewson [Instruct. Sci. 13, 1-13 (1984)]. Four basic concepts for which many students enter the class with alternative conceptions were treated in fall 1995 and fall 1996 in two sections taught by the same instructor. In fall 1995, in one section all four concepts were taught using the collaborative group approach and the other by standard professor-centered methods. In fall 1996, two sections were taught in section A using the collaborative group approach and in section B by standard methods. The other two concepts were taught in section B using the collaborative group approach and in section A by the standard professor-centered technique. (Subject matter in the traditional section was delivered using lectures, but delivery of concepts in both sections was supplemented with interactive computer programs, video disks, and VCR based materials.) Statistically significant greater conceptual change occurred in the treated groups compared to the control groups.