Pillow talk can be expensive; it can cost you your life, the CIA has warned its secret agents around the world. The danger, of course, is AIDS.

The problem is that, unlike officials of other, less devious agencies, the CIA brass hats can't take the straight-arrow approach and urge their spies: "Just say no." The CIA is well aware that an undercover agent is sometimes exactly that, extracting information from susceptible, seducible targets who get carried away in the passion of the moment.

Even the KGB's notorious Delilahs must be growing a little nervous these days as the AIDS epidemic spreads inexorably throughout areas of East-West confrontation.

Faced with this mission-versus-medicine dilemma, the CIA's Office of Medical Services has come down on the side of protection.

"AIDS is 100 percent preventable," secret agents and other employes were assured in a bulletin issued in June. "Scientists who study the transmission of disease point out that the pattern of HIV (human immunodeficiency virus, the current name for the virus) dissemination has been well investigated, and the virus relies entirely on sexual contact, parenteral infusion or perinatal circumstances. Were it otherwise, the types of patients seen would be different."

So, the CIA medical bulletin explained, "while an AIDS vaccine or a disease cure is not yet a reality, preventive measures are very effective."

The bulletin offered seven precautions agents can adopt.

The first rule: "Do not participate in unprotected vaginal intercourse unless it is within a stable relationship; otherwise use condoms and spermicide." But this could easily rob the boudoir opportunity of the very spontaneity that has disarmed the quarry.

Second: "Avoid any intercourse with high-risk individuals or individuals from high-risk areas of the world." Following this sensible advice would place Africa and most of Europe off limits, as well as rule out gay men and intravenous drug users.

Third: "Do not accept any transfusion of blood or any blood product that has not been screened for AIDS." That's fine if the agent needs a pint of blood in Switzerland, but not in a Third World clinic where doctors have neither the equipment nor know-how to test for AIDS antibodies.

Fourth: "Do not accept any treatment involving a needle or injection unless you are certain the facility uses sterile disposable needles." Again, this is a bit unrealistic in many parts of the world.

Fifth ("Avoid unprotected anal intercourse") and sixth ("Be aware that oral-genital contact carries a risk of transmission") offer no special obstacles to the clever spy, while Rule No. 7 is merely common sense: "In a situation where a potential sex partner may be infected, assume they are."

In short, the CIA bulletin warns: "Know your partner."

In the espionage game, the idea is to get to know your target well. But asking a potential paramour to take a test for the AIDS virus may not be an agent's most productive followup to "What's your sign?"