Purpose. To compare the One-Minute Preceptor (OMP) and traditional models of ambulatory teaching in terms of the preceptors' (1) ability to correctly diagnose patients' medical problems, (2) ability to rate students' skills and confidence in doing so, and (3) satisfaction with both models. Method. A within-groups experimental design study was conducted with 116 preceptors at seven universities in 2000. Participants viewed scripted, videotaped precepting encounters of both models using two cases and were asked to rate students' abilities, their confidence in rating the students' abilities, and the effectiveness and efficiency of the teaching encounters. Results. Preceptors who viewed the videotapes of the OMP model were equally or better able to correctly diagnose the patients' medical conditions than those viewing the traditional model. Preceptors viewing the OMP rated students' abilities higher on history taking/physical examination, presentations, clinical reasoning, and fund of knowledge than did those viewing the traditional model. Preceptors viewing the OMP rated themselves as more confident in rating students' abilities in presentation, clinical reasoning, and fund of knowledge. Preceptors rated the OMP as more effective and more efficient than the traditional model. Conclusions. Preceptors viewing scripted, videotaped teaching encounters using the OMP model were equal to or better able to correctly diagnose patients' medical problems, had greater self-confidence in rating students, and rated the encounter as more effective and efficient than when viewing the traditional model.