Joseph Arthur Muldoon Jr., attorney and consummate horsemen, died on March 16 at his home after a long battle with cancer. He was 76.

Mr. Muldoon graduated from Georgetown University School of Foreign Service (D.C.) in 1952 and was awarded his bachelor of laws degree from Georgetown University Law Center in 1955. In 1968, he founded Sloane & Muldoon, the first private law firm specializing in thrift regulation and the representation of financial institutions before the government financial regulatory agencies. Mr. Muldoon retired from law in 2005.

As an avid horseman, Mr. Muldoon was involved with foxhunters, show hunters, open jumpers and polo. He entered his horse, Electrify, in the first grand prix of the United States, ridden by Marlene Allen.

In 1964-65, Joe Fargis rode many of Mr. Muldoon’s show hunters, including Psyche, Secret Agent and Spanish Sea. Allen would later take over the rides, in addition to riding his point-to-point horses, such as War Lord II, on whom she won five races in one year.

With his wife, Alyse, Mr. Muldoon continued breeding and training horses for show careers, all while traveling to show from Wellington, Fla., to the Hamptons (N.Y.).

In 1970, Mr. Muldoon purchased two polo ponies and began his polo career. He began playing with Tommy Dowd, owner of the Potomac Polo Club in Travillah, Md. After Mr. Dowd retired, Mr. Muldoon took over the position and later moved the club to a larger facility in Poolesville, Md.

Dominating the sport in the Washington area, Mr. Muldoon remained a successful polo competitor and promoted the growth of the sport. He was instrumental in introducing high-goal polo to the Washington Metropolitan area, raising the level of club play from six-goal to 12- to 18-goal. From 1981-89, he personally brought players from all over the world to the Potomac Polo Club, where they hosted the first games over 30 goals in the United States since World War II.

Besides the many charity polo matches on his own fields, Mr. Muldoon also helped launch the Family House Charity Polo Match 25 years ago in Pittsburgh, Pa. The organization has raised almost $3 million dollars to date to help families of people who come to Pittsburgh for organ transplants.

Mr. Muldoon’s survivors include his wife, Alyse B. Muldoon; children Joseph A. Muldoon III, Mary Louise Muldoon, Charles Muldoon, Greg Ford, Lanah Hamilton, Tristan Hamilton and the late Michael Muldoon; sisters Mary Elizabeth Muldoon and Patsy Muldoon Murphy; and one grandchild.

Memorial contributions may be made to the Polo Training Foundation, 70 Clinton Street, Tully, NY 13159.