Effects of a computerized professional development (PD) program were investigated in two studies. For each, teachers were randomly assigned to either a Virtual Workshop (VW) group that used a computerized program for PD or to an Actual Workshop (AW) group that participated in a live PD session. In Study 1, the teachers' knowledge about and planning for use of a concept comparison routine significantly improved after completing either workshop. Further, Knowledge Scores earned by the VW group were significantly higher than those of the AW group. In Study 2, both groups of teachers' knowledge about the routine, planning for the routine, and implementation of the routine in classrooms significantly improved, as did the concept acquisition of their students with and without learning disabilities. Implementation scores earned by the VW teachers were significantly higher than those of the AW teachers. Students were satisfied with the instruction provided by both teacher groups. All teacher groups in both studies were satisfied. Implications are discussed. (Contains 1 endnote, 2 tables, and 6 figures.)