Fecundity and size at sexual maturity were investigated in 486 bigeye grenadier, Macrourus holotrachys caught as bycatch in the Patagonian toothfish longline fishery conducted around South Georgia. Macroscopic and histological investigations revealed that absolute fecundity ranged from 22,000 to 260,000 eggs, a relatively high number for a macrourid. Mature ovaries were found to contain eggs at different stages of development suggesting that M. holtrachys may have an extended spawning season. Analyses of size at sexual maturity indicate that Lmat 50 occurs at 29cm (pre-anal length) whilst Lint 50 occurs at 20.57cm. The large difference between these values strongly suggests that yolk deposition and final ovarian development is a prolonged process in M. holotrachys which probably lasts for a period of greater than a year. Sex ratios of specimens caught in the longline fishery are highly skewed with females outnumbering males by a ratio of 32:1 which may represent the true ratio of females to males within the population or could suggest that females are more susceptible to capture by longlines than males.