HONOLULU -- Foreign investors now own 75 properties in the Washington area, including 64 District office buildings that account for one-fourth of all the city's office space, according to a new study of foreign investment in U.S. real estate.

In all, the foreign investors, led by the Japanese, the British and the Canadians, have bought 13 million of the 52 million square feet of office space in downtown Washington, a figure that is steadily growing, according to the study by the Massachusetts Institute of Technology's Center for Real Estate Development.

The survey, which depicts a more substantial foreign presence in the Washington real estate market than previously documented, said foreigners have been attracted to the nation's capital in part because they believe that investments there amount to "inflation-protected annuities."

"Foreign investors are eager to stake out positions in the Washington market because of its overall size and the good prospects for continued tightness {in the commercial real estate market} because of recently high {office space} absorption rates," the report said.

As more and more foreign investors have staked a claim to Washington property, the price for prime downtown real estate has escalated, with foreigners often outbidding American investors, including prominent downtown D.C. developer Oliver T. Carr in one case. Despite the high prices, office rents have risen only modestly or not at all in the last year, the MIT researchers said.

The study, commissioned by the National Association of Realtors and released this week at the trade group's annual convention here, concluded that "what seems to be driving the price increases is investor optimism on the continued fundamental strength of the Washington market ... {and} Washington's historical strength in the face of national economic downturns."

The report said British interests, which have been buying Washington office buildings for several years, own the most buildings in downtown D.C. with 22 totaling 3.1 million square feet of space. But the researchers found that a more recent entrant in the high-stakes Washington real estate market, the Japanese, have bought more space -- 3.6 million square feet in 12 buildings. Two years ago, the Japanese did not own a single D.C. building.

The report said Dutch interests have bought seven District buildings, the Canadians six, the West Germans and Saudi Arabians three apiece and investors from other countries the remainder.

In the Washington suburbs, the MIT study found that foreigners have bought 11 properties -- one in Bethesda and the other 10 in Northern Virginia. Almost all of the foreign-owned properties in the Washington area are office buildings, although some residential and retail space has also been purchased.

The researchers said foreigners prefer to buy downtown D.C. office space in part because of the lack of supply constraints in the Washington suburbs, which do not have the land and building height limitations of downtown Washington.

But foreigners who have bought properties in the District told the researchers they mostly prefer the downtown locations because of their real estate experience in their own countries. Most office buildings in foreign capitals are downtown.

The foreign real estate purchases in the District and its suburbs are part of a nationwide wave of foreign real estate acquisitions that have steadily mounted during the 1980s.

Most real estate industry experts, including the researchers for the Realtors' group and MIT, have attributed the buying spree to a continuing belief in the strength of the United States as a safe haven for investment and because the plunging value of the U.S. dollarhas made American real estate a relative bargain compared with similar investments overseas. Another key factor is simply that foreigners can achieve much higher rates of return on American real estate than they can on property in their own countries, often 5 percent to 7 percent or more on their U.S. investments compared with one-third that amount overseas.

Foreign real estate purchases in the United States may total $6 billion to $7 billion this year, but could jump to $10 billion next year, according to John A. Tuccillo, the Realtor group's chief economist.

Thus far, he noted, the foreign invasion has been restricted to the East and West coasts of the United States, with the vast majority of the foreign purchases taking place in Los Angeles, San Francisco, New York, Boston and Washington, along with substantial Japanese purchases in Hawaii.

The MIT researchers found that more than 51 percent of the downtown office space in Los Angeles is now foreign owned, while only 7 percent of Chicago office space is owned by investors not from the U.S. or Canada.

"Unlike the coastal cities, which benefit from a constant flow of foreigners and foreign investors," the MIT researchers said, "Chicago is in some ways hidden within America's heartland."

The Japanese have been the most prominent foreign players in the buying of America in the last few years, making huge purchases. In one deal, Mitsui Fudosan, a real estate development firm, paid $610 million for the Exxon Building in New York City. The Japanese company's offer was at least $30 million higher than the one by the next highest bidder, according to sources familiar with the deal.

As real estate economist Stephen E. Roulac said here this week, "It's been said the difference between men and boys is the price of their toys. The Japanese toys are U.S. buildings."

While such purchases have been the most publicized, the Japanese have gained an even more substantial foothold in Hawaii. For 20 years they have been buying hotels and, at last count, own about one-fourth of the 66,000 hotel rooms in the state, including huge numbers along Waikiki Beach.

Originally the Japanese just bought hotels here, but now they have started hotel construction as well. One firm, Kumagai Gumi, through its local subsidiary, KG Hawaii Corp., has begun work on the West Beach project several miles from the Pearl Harbor naval base.

When finished, 642 acres of mostly scrub land will be transformed into a resort and urban development with 5,500 hotel and condominium units, 3,700 apartments, a marina, golf courses, lagoons and parks.