He studied science, but family loan led him into the world of banking.

Dunson Cheng was supposed to be a scientist, not the chairman, president and chief executive of the first commercial bank in L.A. to cater to Chinese-Americans.

Born in Vietnam 61 years ago and raised in Hong Kong, Cheng earned a bachelor's degree in applied mathematics and physics at the University of Wisconsin and a doctorate in physics at State University of New York.

He also was an engineer at Xerox Corp. where he designed and fabricated micro-processors for copy machines.

However, when his parents, who had emigrated from Hong Kong to California, got a loan from Cathay Bank to open a restaurant, he was exposed to the banking world. Then, as his family moved into real estate development, financed by the bank's loans, his involvement grew to the point where he was appointed to Cathay's board. Finally, when the bank's president retired in 1985, Cheng was brought in as his successor.

"Science trained me to think logically and analytically, and that was helpful when I moved into banking," the Glendale resident explained.

Cheng's brand of financial science has worn well.

In 1999, Cathay Bank purchased Golden City Commercial Bank in New York City's Chinatown, adding nine branches to the 30 it ran in California. Cheng has overseen the opening of branches in Seattle and Boston, and next month he expects to get final approval for the purchase of a Chicago-area bank. That's a far cry from Cathay's start in a modest 1,000-square-foot storefront in Chinatown with $550,000 in capital. Today the publicly traded Cathay General Bancorp Inc. lists assets of $7.4 billion.

Increasing its profile in all the major Chinese-American markets has been key to Cathay's expansion plans. But it's hardly the only area of growth.

"Our style of banking is almost like two separate industries," Cheng said. "More than 80 percent of our business on the deposit side is retail to Chinese-Americans. But the bulk of our lending is commercial."

Cheng also has steered Cathay Bank into overseas markets, investing in a Shanghai bank and opening offices in Talpei and Hong Kong; but it's mostly to facilitate his L.A.-based importers who spend tens of millions of dollars each year bringing in Chinese-made goods.