Petit collaborated with Constant Lambert (Ballabile - 1950), Henri Dutilleux (Le Loup - 1953), Serge Gainsbourg, Yves Saint-Laurent and César Baldaccini and participated in several French and American films.

He continued to direct ballets for the largest theatres of France, Italy, Germany, Great Britain, Canada and Cuba.

He resigned by letter from home (because he had no telephone in his office) protesting about poor working conditions, the failure in labour contract negotiations, and thwarting of his plans for three new ballet productions of which management only accepted one.

He collaborated also with the nouveaux réalistes including Martial Raysse, Niki de Saint Phalle and Jean Tinguely.

Le jeune homme et la mort ("The Young Man and Death") of 1946 (libretto by Jean Cocteau) is considered his magnum opus and it is also his most well-known work; the choreography and the costumes are of astonishing modernity.