With concrete barriers going up at the White House, fear of political terrorism has spread throughout the land, prompting business executives to give more serious thought to matters of personal safety. Scores of new security companies have emerged, catering to the corporate market. At the same time, the handful of larger companies that offer a range of security products are seeing their sales grow impressively.

Whether or not terrorists pose any clear and present danger to American businesspeople is another question. The incidence of terrorism in the United States has actually declined over the past three years. "Public awareness of terrorism is increasing," says Manuel Marquez Jr., a special agent at the Federal Bureau of Investigation. "The perception that there exists a greater threat in this country, however, is not in line with reality."

Yet the fear of terrorism is palpable -- and profitable -- all the same. Witness Newmayer Industries Inc., of Salinas, Calif., a maker of armored cars. Founded in August 1983 the company expects sales to reach at least $2 million by the end of its first 12 months. The company's cars are American sedans that have been made completely bulletproof and strengthened to resist bombs; they cost about $87,000 each. "The armored-car market has broken wide open," says Rickey Newmayer adding that he expects at least six new armored car manufacturers to enter the market by the end of the year.

The bodyguard business is likewise booming. Sales at New York city -- based Security Experts Inc., for example, have increased 100% a year since its founding in 1979, according to president James Motherway. The agency, staffed by some 200 ex-police officers and detectives, had revenues of about $3 million in 1983.

"Terrorism was once thought restricted to Western Europe," observes Motherway. "But the constant play it gets in the newspapers these days has made everyone afraid of it." In an effort to cash in on that fear, Security Experts recently came up with a rather off-beat -- some might say ghoulish -- marketing device: a bodyguard gift certificate. for $150, plus out-of-pocket expenses, the company will assign an armed plainclothesman to the lucky recipient for an eight-hour period of his or her choice.

For those who prefer to guard themselves, there is an impressive array of sophisticated surveillance gadgets and personal protection devices available from companies like CCS Communication Control Inc., a security company in New York City. Its catalog offers such items as bulletproof briefcases that can be used as shields, portable metal detectors, explosive detectors, bulletproof clothing, and remote-control devices that allow customers to start their cars from a half-mile away. The company also sells a small transmitter a user can wear in his belt and switch on if he has been kidnapped, enabling police to track him down. If all this sounds like the stuff of cheap novels, consider that the $30-million company has seen its sales triple in the past three years.

Meanwhile, other companies have diversified their product lines to get a slice of the antiterrorist market. MinXray Inc., of Evanston, Ill., is a case in point. A small manufacturer of portable X-ray devices, the company has traditionally marketed its products to the medical, dental, veterinary, and podiatric professions. In the past five. years, however, it has found eager customers in government and industry, and its security business has doubled. Says MinXray vice-president Keith Kretchmer, "With the increasing number of bombings around the world, more and more companies are buying X-ray equipment for things like inspection of mail and hand-carried packages" -- rather than, say, medical diagnosis.

And that, in the final analysis, may well be the saddest commentary of all.