A cost analysis of the most economical AT&T common-carrier, land-line networks for broadcasting biomedical information to the U.S. biomedical community, via ETV, and to medical schools, via closed circuit TV. The cost estimates are based on standard AT&T rates. The "minimal weighted spanning tree" algorithm was programmed on JOSS to calculate the least-cost network. A 106-station ETV network to serve over 97 percent of all active U.S. physicians living in Standard Metropolitan Statistical Areas would require 12,000 miles of intercity line. The total cost per hour would be $80,000 for a one-hour and $27,000 for a five-hour broadcast; costs per potential viewer-hour would be 30 and 11 cents, respectively. All 97 medical schools could be served by 72 local AT&T Program Operating Centers using 10,000 miles of intercity line. To broadcast 160 hours a month to 85,000 students and staff in 97 medical schools, the cost is $6000 per school, $7 per potential viewer, and 5 cents per potential viewer-hour. 88 pp. Ref.