Changes in conductivity with repeated fabric extension were investigated to improve the properties of conductive electrode pad material used for electrotherapy when it is subjected to various movement of human body. Highly stretchable and conductive fabrics were prepared by in situ chemical polymerization of polypyrrole on nylon-spandex stretch fabric in aqueous solutions with 0.5 M pyrrole, 1.165 M FeCl3, and 0.165 M benzenesulfonic acid at 5degreesC for 1 h. Performance of prepared stretchable conductive fabric was evaluated in terms of conductivity changes as a function of tensile strain, repeated extension, and current application time. As the degree of extension increased, the conductivity increased and leveled off when the fabric was subjected to 60% extension. The number of fiber contacts in nylon-spandex fabric with electrode increased as the applied extension increased. However, the conductivity of the composite decreased under excessive extension over 60% since the intrinsic elasticity of fabric became gradually reduced. Generally, the fabric conductivity decreased as the number of extension cycles increased. However, the fabric conductivity was well maintained after repeated extension over 30 cycles at 40% extension. In addition, it was found that the effect of charging during the electrotherapy treatment on a current flow through prepared electrode pad was negligible. (C) 2003 Wiley Periodicals, Inc.