Different types of conductive polymers have been synthesized within the pores of microfiltration membranes. These membranes contain linear, cylindrical pores of varying diameter from 10 nm to 10 mu m. The polymerization conditions in such pores are quite different from polymerizing on a flat surface, and are therefore investigated. It is shown that the geometry for the smaller pores results in a situation where the concentration of radicals is low compared to the concentration of monomers, resulting in a material with higher conductivity. The bulk concentration of monomers is also a crucial aspect, where higher concentrations give polymer fibres with higher conductivity.