An advertising agency is an independent organization composed of creative and business professionals. The agency develops and prepares market plans, advertisements, and other promotional plans for its clients. Some major advertising agencies in India include Ogilvy & Mather Ltd, Mullen Lowe Lintas Group, GWT Hindustan Thompson Associates, Rediffusion – DY&R, Mudra Communications Ltd, and McCann-Erickson India Ltd. The document then discusses the organizational structure of advertising agencies and their functions before concluding with evaluating agency performance.