Peter W. Stroh, a former chairman of the Stroh Brewing Company, died on Tuesday at his home in Grosse Pointe Farms, Mich. He was 74. The cause was brain cancer, said Mr. Stroh's cousin, John Stroh III. Mr. Stroh was a philanthropist and conservationist whose family fortune was built on decades of selling modestly priced beer to working-class customers in the Midwest. From the company's headquarters in Detroit, Mr. Stroh engineered a series of acquisitions in the 1980's as he tried to remake the company into a national power. Mr. Stroh's company failed in the two fast-growing niches of an industry that was otherwise stagnating: light beer and the so-called superpremium segment. As brewing giants like Anheuser-Busch, Miller and Coors developed strong national brands, Stroh's fell ever farther behind. Soon after Mr. Stroh joined the company's highest ranks, it began to acquire other big brewers. The company bought the F&M Schaefer Brewing Company in 1981 and it acquired the Jos. Schlitz Brewing Company the next year. In 1999, two years after Mr. Stroh retired, the company sold its breweries and brands to Miller and Pabst, another big beer maker, for about $400 million. Mr. Stroh did not originally want to join the family business, which was founded in 1850 in Detroit by his great-grandfather. After graduating from St. Paul's School in New Hampshire in 1945 and from Princeton University in 1951, Mr. Stroh was recruited by the Central Intelligence Agency. Mr. Stroh spent a year in Washington waiting for security clearance. Three days after his final clearance was approved, Mr. Stroh's legs were crushed by a truck in a Washington intersection. He spent a year in a hospital and limped for the rest of his life. Unable to join the C.I.A. because of his injury, Mr. Stroh returned to Detroit. He joined the brewing company in 1952 and became a director in 1965, soon after he married the former Nicole Elisabeth Fauquet-Lemaitre. Mr. Stroh is survived by his wife; two sons, Pierre, of Grosse Pointe Farms, and Frederic, of Washington, D.C.; a brother, Eric, of Grosse Pointe Farms; and one grandchild.