BACKGROUND: Providing midclerkship feedback to identify students at risk for failing is a Liaison Committee on Medical Education standard. Objective criteria for that feedback are critical. The investigators studied the value of a formative midterm (MT) test in identifying students at risk for failing a surgery clerkship. METHODS: A written midclerkship test, which did not contribute to the final grade, was administered (n = 155). The Bayesian specificity, sensitivity, and predictive values for clerkship failure of low MT score, low global clinical performance rating GCPR, and the combination of low MT and low GCPR were computed. RESULTS: Low MT as a predictor of clerkship failure was sensitive (1.0) but not specific (.35). Likewise, low GCPR was sensitive (1.0) but not specific (.31). The combination of low MT and GCPR, however, was both specific (1.0) and sensitive (.87). CONCLUSIONS: The addition of an MT test to clinical performance ratings can stratify students' risk for clerkship failure.