The transport of positive charges along porphyrin-based molecular wires has been probed in dilute solution using pulse radiolysis time-resolved microwave conductivity. The mobility of positive charges along isolated single-strand porphyrin wires was found to be 0.084 cm(2)/(V s). Addition of 4,4'-bipyridyl leads to the formation of a double-strand ladder complex, locking each polymer strand into a more planar structure and thus enhancing the porphyrin-porphyrin pi-conjugation, leading to an increase in the charge carrier mobility by an order of magnitude to 0.91 cm(2)/(V S).