From several studies of transport properties of conducting polymers (CP) as
a function of a parameter related to their structure or microstructure we
show that in strongly disordered CP, electron transport is dominated by hop
ping between conducting grains separated by insulating barriers. In CSA-pro
tonated polyaniline, a weakly disordered CP which exhibits a metallic-like
behaviour, several results indicate that heterogeneities play a major role
in the transport process. Thus, we conclude that heterogeneous disorder app
ears as a key parameter which controls the conductivity of a large majority
of CP.