Dennis Ralston, a five-time Grand Slam doubles champion who was one of the first players signed to the professional World Championship Tennis tour in the 1960s and a member of the sport’s Hall of Fame, died on Sunday in Austin, Texas. He was 78.

Darin Pleasant, director of tennis at Grey Rock Tennis Club in Austin, where Ralston was on the teaching staff, confirmed the death.

As a singles player, Ralston lost to Manuel Santana of Spain in three sets in the 1966 Wimbledon final. He reached the semifinals at the 1960 U.S. national championships and the 1970 Australian Open. He was considered the highest-ranked American player for three years in the 1960s, long before the sport’s computerized rankings system began.

But Ralston found his greatest success in doubles. He paired with Rafael Osuna of Mexico to win Wimbledon in 1960 as a 17-year-old. He and a fellow American, Chuck McKinley, won titles at the U.S. national championships in 1961, ’63 and ’64. And Ralston teamed with the American Clark Graebner to win the 1966 French championships on clay. He was a three-time Grand Slam finalist in mixed doubles.

Ralston was one of the so-called Handsome Eight who signed on with the WCT tour in 1967, along with John Newcombe, Tony Roche, Cliff Drysdale, Earl Buchholtz, Niki Pilic, Roger Taylor and Pierre Barthes. The circuit began the next year and lasted until the emergence of the current ATP Tour in 1990.

The WCT tour helped commercialize the sport, instituting a tiebreaker system and emphasizing its prize-money structure and a bonus pool to attract top players. The WCT encouraged players to wear colorful clothing and fans to cheer, moves that shook up the staid atmosphere of tennis.

Richard Dennis Ralston was born on July 27, 1942, in Bakersfield, Calif. He attended the University of Southern California, helping the Trojans to N.C.A.A. titles in 1962, ’63 and ’64, when he also won the N.C.A.A. doubles title.

Ralston turned pro after his runner-up finish at Wimbledon in 1966. He had a career singles record of 576-251 and won 41 titles. His career mark in doubles was 125-87. He retired in 1977 and was inducted into the International Tennis Hall of Fame 10 years later.

Ralston helped the United States win the Davis Cup title in 1963. He captained the team from 1972-75, including in its 1972 win over Romania in the final.

The Davis Cup was the beginning of Ralston’s coaching career. He spent six years coaching Chris Evert, including the early years of her burgeoning rivalry with Martina Navratilova.

Other pros he coached include Roscoe Tanner, Yannick Noah and Gabriela Sabatini. He had two stints as men’s coach at Southern Methodist University in Dallas in the 1980s and ’90s. He spent the last decade at Grey Rock Tennis Club.

After decades of playing tennis, Ralston had both knees replaced in the late 1990s. He played in the seniors tournament at Wimbledon after his second surgery. He later had foot problems, and a series of infections forced the amputation of his left leg below the knee. But wearing a prothesis, he continued to play U.S.T.A. league tennis. Being in constant pain led to an addiction to painkillers, which Ralston discussed publicly. He overcame that dependence after a stint at the Betty Ford Center in Rancho Mirage, Calif.

He is survived by his wife of 56 years, Linda; a son, Mike, and two daughters, Lori and Angela.