The electromechanical actuation performance of carbon nanotube mats, polypyrrole films and hybrid nanotube-polypryrrole materials has been compared. The hybrid materials were formed by coating nanotube mats with polypyrrole using vapour deposition and electropolymerisation techniques. When the coating time was short, the hybrid materials showed the electrochemical responses typical of polypyrrole and retained the porous structure of the nanotube mats. The actuator response of the different materials was determined isotonically at different applied loads. The nanotube mat and hybrid materials gave actuator strains that were largely insensitive to the applied stress up to ∼ 10 MPa. The hybrid materials were virtually identical to the uncoated nanotube mats in terms of actuator performance. A simple model showed that the actuator strain depends upon the difference in elastic modulus of the actuator material in the doped and undoped states. © 2001 SPIE - The International Society for Optical Engineering.