Electrorheological (ER) and magnetorheological (MR) fluids based on electro- and magneto-responsive particles, respectively, are smart suspensions with the ability to undergo phase transitions from a liquid-like to a solid-like state as a result of stimuli of an electric or magnetic field. The application of polymer composite materials rather than pure polymeric or inorganic materials is aiming to solve the problems in the use of both ER and MR materials, such as low activity, physical and chemical stability, and production cost. Various fabrication methods of polymer composite materials with electro-activity or magneto-activity developed and effectively applied in this field to boost the wide commercialization of both ER and MR fluids are briefly reviewed in this perspective. (C) 2012 Society of Chemical Industry