Survey data from a sample of 58 U.S. and six Canadian medical schools were used to describe the current network of medical schools and their affiliates. Results showed that each medical school in the study averaged over 11 affiliates. The largest percentages of affiliates reported were in the categories of "community" hospitals (that is, the nongovernmental, not-for-profit hospitals), Veterans Administration hospitals, and city hospitals. Characteristics of the medical schools, such as class size, ownership, year established, and the presence of a university hospital, were not related to either the number or the kind of affiliates. However, the sizes of the affiliated institutions were associated with the year the medical school was established, the presence of a university hospital, and the class size of the medical school.