Vlastimil Koubek, 75, one of Washington's most influential architects whose work on nearly 100 offices, hotels and apartment buildings since the late 1950s helped to shape the city's skyline, died of cancer Feb. 15 at his home in Arlington.

Mr. Koubek's buildings include the headquarters of the National Bank of Washington, the American Security Bank, the Union Labor Life Insurance Co., the American Automobile Association and the Postal Service.

He was the lead architect for L'Enfant Plaza's east building, the International Square building and the renovation of the Willard Inter-Continental hotel and office building in the mid-1980s.

In 1985, Washingtonian magazine named Mr. Koubek one of 20 notable Washingtonians "who in the past 20 years had the greatest impact on the way we live and who forever altered the look of Washington."

He left his mark in other cities as well.

He designed the 40-story U.S. Fidelity and Guaranty Life Insurance Co. headquarters in Baltimore and the 22-story Virginia Electric and Power Co. headquarters in Richmond.

He also worked on buildings in Charleston, W.Va., Wilmington, Del., and Miami.

Mr. Koubek, who became an authority on drafting construction documents for commercial buildings, studied architecture in his native Czechoslovakia.

He came to the United States in 1952 and served two years in the U.S. Army.

He worked briefly for a New York architectural firm, then moved to Washington, where he opened Koubek Architects in 1957.

During the Nixon administration, Mr. Koubek served on the General Services Administration architectural advisory panel.

In the summer of 1984, he helped inspect housing for Foreign Service officers living in Europe and Asia, with special emphasis on security.

His marriage to Eva Koubek ended in divorce.

Survivors include his wife of 19 years, Peggy Koubek of Arlington; and a daughter from his first marriage, Jana Koubek of Washington and Albuquerque.