Competent performance requires not only requisite knowledge and skills but also beliefs of personal efficacy to use both effectively. This study examined the confidence of second-year medical students regarding their OSCE performance. Students completed an OSCE at the end of their second year of medical school; their performance was rated using checklists containing key items. Ten minutes prior to the OSCE, students completed a brief survey, which included 31 items sampling confidence in performing various clinical skills required in the OSCE. In addition, students assessed their preparedness and their anxiety, and reported the number of hours they studied in preparation for the OSCE. A total of 82 identifiable surveys (73 %) were used in this analysis. Students with high self-efficacy were more likely to score above the mean OSCE performance compared to low self-rated students (71% versus 51%), however self-efficacy was not significantly correlated to OSCE performance. A causal path model was constructed to predict OSCE performance. Performance in the clinical skills and biomedical science curricula both were related to perceived anxiety, which was related to self-efficacy. Preparedness was predicated on self-efficacy and itself predicted performance. Knowledge also had a strong direct link to performance. Performance is more than having the requisite abilities. Performance was found to be the product of complex relationships between skills and knowledge, mediated by perceptions of anxiety, self-confidence and preparedness. The model illustrates the importance of realistic self-appraisal for competent performance.