Micro-coiled carbon fibres were prepared by the transition metal-activated pyrolysis of acetylene containing a small amount of sulphur compounds, and the preparation conditions were examined in detail. The coiled carbon fibres grew at the reaction temperatures of 700-850 degrees C and thiophene gas flow rates of 0.14-0.45 standard cm(3) min(-1) (0.10-0.35 vol% reaction atmosphere). The optimum values depended on the type of metal catalysts used. Among the metal catalysts used, nickel, titanium and tungsten were the most effective for the growth of the coiled carbon fibres and a maximum yield of about 50%-55% was obtained. The bulk resistivity of the coiled carbon fibres decreased with increasing bulk density and was 10(0) S-1 cm at a bulk density of 1.