Susan Thompson Buffett, 72, the wife of billionaire investor Warren Buffett and, in her own right, the 17th richest woman in the world, died July 29 of a stroke while visiting friends in Cody, Wyo.

She and Buffett, whose net worth of about $41 billion makes him the second richest man in the world after Bill Gates, were married in 1952 but had lived apart since 1977. Her primary residence was in San Francisco, while he stayed in the house they had bought together in Omaha in 1958. They remained on friendly terms and often traveled together. Warren Buffett was with his wife at a Cody hospital at the time of her death.

Mrs. Buffett was a director of Berkshire Hathaway, her husband's holding company, and was president of the Buffett Foundation, which has contributed millions of dollars for education, medical research, population control and other charities. The foundation was criticized by abortion protesters in the 1990s for funding the RU-486 "abortion pill" and groups supporting abortion rights.

She was known for her progressive views, had worked for civil rights and volunteered to help people in low-income housing. In evaluating organizations for possible contributions, Mrs. Buffett told the Omaha World-Herald last year in a rare interview, she sought people "who have heart and soul, the ability to organize and also to inspire -- a rare combination."

Her shares in her husband's company have a current value of about $3 billion, which made her, according to Forbes magazine, the 68th richest person in the United States.

Last week, Mrs. Buffett and her husband contributed $6 million to five California doctors for the study of mouth cancer. In October 2003, Mrs. Buffett was diagnosed with mouth cancer and underwent surgery, radiation therapy and facial reconstruction. She had recovered enough to attend the annual shareholders' meeting of Berkshire Hathaway in May, leading singalongs at cocktail parties.

She also attended her granddaughter's graduation this spring from her alma mater, Omaha Central High School. She donated $5 million to the school two years ago for a new stadium and had given to many other institutions in her home town, as well.

Like her husband, Mrs. Buffett was born and raised in Omaha. Her father was a college professor and dean. Though their parents were acquainted, she did not meet Warren Buffett until her roommate at Northwestern University -- his sister, Roberta Buffett -- introduced them.

She occasionally performed as a cabaret singer and, in 1977, had a one-night performance at an Omaha theater. Soon after, she left her husband and moved to San Francisco, saying she wanted to pursue her singing career. She performed in New York and released several CDs. According to Roger Lowenstein's biography, "Buffett: The Making of an American Capitalist," her husband was heartbroken by her move. Since 1978, he has lived with Astrid Menks.

In a rare interview in 1999 with the Omaha World-Herald, Mrs. Buffett described herself as a "geriatric gypsy," saying she spent only 20 percent of her time at her home in San Francisco.

She had been in line to inherit her husband's fortune, but with her death nearly all of his wealth will go toward creating a charitable foundation. At current rates, the endowment of more than $40 million would make it wealthier than the Gates Foundation, which is currently the largest in the world.

Survivors include her husband, of Omaha; and three children; and several grandchildren.

Susan T Buffett