Last year, only 6 percent of 6.6 million military beneficiaries with prescriptions to fill used the low-cost Tricare Mail Order Program. By contrast, 51 percent had at least one prescription filled through Tricare's more costly retail network.

That means that many thousands of beneficiaries pay more than necessary for medicines, said Capt. Thomas J. McGinnis, chief of Tricare's Pharmaceutical Operations Directorate.

It also means the Defense Department pays many millions of dollars more than it should for drugs. Every prescription filled in Tricare retail outlets, which reached 50 million last year, costs the government 30 percent to 40 percent more than mail order.

McGinnis is leading the first-ever campaign by Tricare to increase mail order use.

It will begin with an effort to educate beneficiaries on the convenience and cost-savings of prescriptions filled by mail. Then, unless Congress intercedes, Tricare will restructure pharmacy co-payments so mail order usage becomes more attractive, and retail less so.

Military pharmacies cost nearly $6 billion a year.

A Public Health Service officer, McGinnis spent 28 years with the Food and Drug Administration. His last assignment was as FDA's director of pharmacy affairs.

"Prescription drug costs are our biggest worry," he said. Expanding the use of mail order is his first priority.

First, he said, beneficiaries need to know that mail order users already save 66 percent on co-payments because prescriptions filled by mail provide a 90-day supply versus 30 days in the retail network.

Second, the government saves on each prescription not filled in the retail network. The reason is that drug stocks on base and for mail order are purchased at federally negotiated price discounts.

A third factor to consider, said McGinnis, is the convenience of mail order.

Generic drugs also lower costs. Tricare has a mandatory generic substitution policy.

Any prescription for a brand name drug must be filled by generic medicine of identical ingredients and strength, if available.

Tricare officials hope to use a change in co-payments not only to encourage more beneficiaries to use mail order but also generic drugs.

The plan would end the $3 co-payment on mail order generics. At the same time, co-pay for the retail network would rise from $3 up to $5 for generic and from $9 up to $15 for brand name drugs.

The company Express-Scripts runs the TMOP. To reach it, call (866) 363-8667, or (866) 275-4732 from overseas; e-mail TMOP.customer.rela tions@express-scripts.com; or write to Express Scripts Inc., P.O. Box 52150, Phoenix, AZ 85072.