This study investigated the impact of a structured exercise on low back pain, as part of a second year ambulatory course, on students' low back pain examination skills. One-hundred and eighty-eight medical students participated in one of four types of instructional intervention: 1) structured clinical exercise and reading, 2) random clinical experience and no reading, 3) reading only, and 4) no clinical experience or reading. At the end of the year, students completed an Objective Structured Clinical Exam (OSCE) in which two stations assessed back pain history and physical exam skills. An analysis of variance of the OSCE scores showed no significant difference in students' performance in relation to the type of instructional intervention. The General Professional Education of the Physician Report argues for the importance of structured clinical education. In medical education, unpredictable patient exposure and crowded curricula frequently result in students having none or only one structured learning opportunity to acquire critical skills. Unfortunately, this study found that assuring at least one structured clinical experience for a specific common problem seen in ambulatory care did not enhance student ability to select and use specific history or physical exam skills for that problem as assessed by an OSCE, as compared with students who did not have this experience. To assure that essential clinical skills are acquired, it most likely requires that both systematic instructional strategies and repeated learning opportunities are available to reinforce learning.