This report describes the 673 medical Critical Health Manpower Shortage Areas (CHMSAs) listed by the Federal Register for February 25, 1975, in terms of the Comprehensive Health Planning (CHP) areas where they are located. It describes how the Rural Health Initiative program is designed to cope with the shortage problem and how this program is related to the work of the Health Service Agencies (HSAs) that are succeeding the CHP councils under the new health planning law. A method for relating CHPs and HSAs in specific areas is indicated. Of the 416 CHPs into which the United States (excluding Alaska and the New England States) was divided as of May 1973, 269 had one or more CHMSAs. In 99, the CHMSAs covered over one-third of the land area. CHPs with very large urbanized areas had relatively few CHMSAs and only 24 CHMSAs contained an urbanized area. On the average, about the same proportion of CHP areas with Standard Metropolitan Statistical Areas (SMSAs) had CHMSAs as non-SMSA type CHPs--63 percent v. 66 percent. CHP areas with socioeconomic variables deviating adversely from the average had a high proportion of CHMSAs. In 112 CHPs, all of the CHMSAs were outside a circle of 50-mile radius drawn around urbanized areas of 100,000 or more; in 102, part of the CHMSAs were outside the circle. Tests made on CHPs with a high probability that CHMSA designation might have been overlooked found few instances of potential omission. However, findings suggest that possibly different criteria are needed for medical service areas characterized by a large land area with very few residents.