He soon became one of the most respected and versatile of ABT's male contingent, excelling in both modern and classical ballets, and was quickly promoted to principal dancer.
The next evening he danced the role of James in the 19th century Danish classic, La Sylphide, by August Bournonville and astounded with his versatility.
Marks ended his performing career in 1976 in Denmark taking on his first artistic directorship with Ballet West in Salt Lake City, Utah.
Under his dynamic leadership, Boston Ballet achieved international acclaim and built a reputation for performing authentic versions of the classics and for encouraging daring modern works.
His time in Boston had many highlights: an unprecedented American/Soviet production of Swan Lake; the company's 1990 debut at Washington's Kennedy Center; a 1991 five-city tour of Spain; and in 1993, to inaugurate its 30th season, a highly acclaimed version of The Sleeping Beauty.
Following a second Kennedy Center engagement in March 1994, Boston Ballet became the first American company to perform John Cranko’s Onegin.
In 1995, Marks added Cranko's The Taming of the Shrew to the company's repertory, followed in 1997 by Michael Corder’s award-winning Cinderella.
As such, he commissioned works by Danny Buraczeski, Bill T. Jones, Ralph Lemon, Monica Levy, Susan Marshall, Bebe Miller, Daniel Pelzig and Lila York.
Marks is a founding member of Dance/USA, a national service organization that represents professional dance companies and from 1990 to 1992 was Dance/USA's chairman.
[11] In 1998, Marks created ArtsVenture, Inc., a consulting firm dedicated to passing along to others the vast knowledge and insights that he has accumulated in the field.
[2] In 1966, Marks married Danish ballerina Toni Lander with whom he had three sons—Erik Antony, Adam Christopher, and Kenneth Rikard.