The cost of medical student instruction in the practice setting.

Using an incremental cost approach, the cost of instruction for medical students participating in a variety of ambulatory-care, chiefly family-practice, experiences in several clinical practice sites was examined. The costs ranged from $5 per student per day for a first-year observational experience to $112 per student per day for a second-year preceptorship with direct patient care involvement by the students. Factors such as the previous experience of the student, the baseline productivity of the site, the number of examining rooms, the income source of the preceptor (salary vs fee-for-service), and the clarity of preceptor role definition are discussed in relation to cost. The lack of defined, stable income to offset costs is noted. In view of the substantial costs of instruction in ambulatory family practice clerkships, clearly defined ongoing sources of income must be provided to ensure the continuation or expansion of these vital experiences.