We derive and apply a model that determines the effective minority carrier lifetime of macroporous crystalline silicon samples as a function of bulk lifetime, surface passivation and pore morphology. Two cases are considered: A layer of periodic macropores at the surface of a silicon wafer and a free standing macroporous silicon layer. We compare the model with experimental lifetime measurements for samples with randomly positioned macropores with a length of 10-40 mu m. The pores have an average pore diameter of 2.4 mu m and an average pore distance of 5.2 mu m. The surface is passivated by thermal oxidation. The model agrees with the measurements if we assume an average surface recombination velocity S=24 cm/s at the pore surface. (C) 2011 Elsevier B.V. All rights reserved.