René Gruaus illustrations were intensely very important in the haute couture world. Haute Couture is a French phrase for high fashion. Couture means dressmaking, sewing, or needlework and haute means elegant or high, so the two combined imply excellent artistry with the fashioning of garments. The purchase of an haute couture model garment is at the top level of hand customized fashion design and clothing construction made by a couture design house. A model haute couture garment is made specifically for the wearer's measurements and body stance.
During Gruau's lifelong career he collaborated with fashion houses such as Givenchy, Balenciaga, Lanvin, Schiaparelli and Dior in the fashion area of haute couture.
René Gruau's advertising campaigns for Moulin Rouge and Lido de Paris utilised an old-world aesthetic, celebrating the traditional poster-art graphics of Toulouse-Lautrec, Bonnard and the pre-1900 Parisian artists. He continued to work in advertising designing the hugely influential cinema poster for Fellini’s La Dolce Vita in 1959 and working on campaigns for names such as Dior, Air France, Martini and Omega watches. He has been exhibited internationally at the Paris Musee du Costume and The Musee de la Publicite.