Paternity was analysed in two domestic cat (Felis catus) populations differing in habitat structure (rural versus urban) and density (234 cats km-2 versus 2091 cats km-2). A total of 312 offspring, 76 mothers and 65 putative fathers were typed at nine microsatellite loci in the two populations. Our data showed a high rate of multiple paternity in the urban population (70 to 83% of litters with more than one father), whereas it was much lower in the rural population (0 to 22% of litters with more than one), as most males were able to monopolize the entire litter. However, males reproduced as soon as they reached sexual maturity (i.e. ten months of age) in the urban population, whereas most males delayed reproduction to age three years in the rural population.