The charge carrier dynamics in illuminated nanoporous ZnO electrodes consisting of 5 nm particles were investigated. Stable photocurrent quantum efficiencies of 15-30% and photovoltages of up to 0.4 V were found in the presence of the I-/I-3(-) redox couple in propylene carbonate. The electronic transport in these ZnO electrodes was fast, the tunneling of electrons from the ZnO particles to the conducting substrate was much slower. The photovoltage as a function of light intensity showed a clear discontinuity. This was related to the indirect recombination kinetics; under open circuit conditions it could take 10 s or longer before a photogenerated electron was transferred to I-3(-) in solution.