Despite a sex ratio approximating to unity, female corn buntings were not equally distributed among males. In 1989 and 1990, 41.2% of 50 males were monogamously paired, 29.4% were polygynous, and 23.5% were unpaired. Polygynous males usually paired with two females, although in 1990 three males were trigamous. Polygynous males fledged more offspring from their territories than did monogamous males, mainly because they had more mates. The fledging success per nesting female was slightly higher in territories of polygynous males, but not significantly so. DNA fingerprinting was used to confirm the true paternity of 44 offspring from 15 broods and the true maternity of 50 offspring from 16 broods. A further 12 offspring from three broods for which neither putative parent was available were also fingerprinted. Actual reproductive success of parents was close to that inferred from observations of number of young raised. There was only one brood, containing two chicks (4.5% of offspring, or in 6.7% of broods), where the chicks were not fathered by the male defending the territory. However, this nest was close to the territory boundary, and the defending male may have been assigned incorrectly. There were no cases of intraspecific brood parasitism (n = 16 broods). The copulation rate was low, and extrapair copulation attempts were rare, probably because of the poor chances of sneaking onto a neighbor's territory undetected and the costs of leaving a territory unguarded.