NEW YORK — FOR many United States companies, marketing products and services directly to Asian-Americans seems as difficult and unknown as selling to Asia itself. But some major corporations instead see Asian-Americans as dynamic and affluent, and they are appealing to them with carefully crafted advertising campaigns.Consumer giants including AT&T, Colgate-Palmolive, Metropolitan Life Insurance, and Citicorp are spending increasing amounts of time and money to address Asian customers - especially Chinese, Koreans, and Japanese. These companies have gone to a handful of specialized advertising agencies, entrusting them to create an identity and demand for their products within this insular, yet heterogeneous, community. One look at recent demographic studies shows why Asian America has become so attractive to corporate America. The group's population jumped from 3.5 million to 7.3 million during the 1980s, according to US Census figures. The number is expected to grow to 10 million by the end of the decade. Furthermore, a high proportion of Asian-Americans are college graduates. They make good money. Their average annual income of $38,450 easily tops the $31,231 that Caucasian Americans brought home on average last year. Perhaps of prime importance, most are newcomers, with little loyalty to any one brand. They also show a desire, common among immigrants, to blend into their adopted culture while honoring traditional beliefs and customs. "Asian-Americans, after moving to this country, have to make an adjustment," observes Joseph Lam, a partner in L3 Advertising, a New York agency that has developed Asian market campaigns for Colgate-Palmolive, Metropolitan Life, and MCI Communications. "They have a strong inner need to be accepted. Any marketer that extends good will or gives an indication that they welcome Asians' business will have a very good first impression." The question for US companies is how to do so effectively. Everette Dennis, executive director of the Freedom Forum Media Studies Center, notes that Asian Americans are a difficult target. "They want to be part of the mainstream, and have their culture recognized," he explains. Because Asian America is far from a collective culture, advertising agencies pay particular attention to individual ethnic backgrounds in their ads. AT&T's television and print campaign to Chinese-Americans, for instance, features well-groomed Chinese actors who could be business owners or professionals, in home and office settings that suggest an upper-middle-class blend of Western and Asian tastes. People from Taiwan and China are pitched in Mandarin; those from Hong Kong hear Cantonese. But the images and values that advertisers use to relay their message to Asian Americans are still largely experimental. CLEARLY, advertisers treat Asian America differently from mainstream America. Ads aimed at most Americans emphasize personal choices, independence, and leisure. Ads aimed at Asian-Americans, in contrast, emphasize family unity as a means to achieve financial success and social status. Because many Asian cultures believe that "the nail that sticks up gets hammered down," ads avoid showy displays of personal wealth and individuality. Eliot Kang, whose New York-based agency, Amko Advertising, created AT&T's Asian marketing, often plays to the respect for tradition that is deeply ingrained in Asians. Many of the commercials he produces focus on corporate stability even more than on the product itself. "The image that every corporation is trying to achieve is that they're big and they have a long history of experience," he explains. Seen another way, the company becomes extended family, caring about the customer's happiness and well-being. Mr. Lam developed an ad for Metropolitan Life that features four children dressed as professionals and wearing oversized clothes. A Korean boy sports a business suit, an Indian child dons a scientist's lab coat, a Filipino girl wears a doctor's outfit, and a Chinese youngster wears a college graduate's cap and gown. The ad encourages customers to "plan your future" with the company. As companies try to plan their own marketing future, their path remains uncertain. History suggests that, even in the most cohesive groups, successive generations will form their own identities. But some experts, including Lam, say the images and approaches to which Asians respond will remain fairly constant, that cultural identity takes precedent over assimilation. "I don't care how many generations you've been in America," Lam says. "You are still a minority."