Ovaries of 39 large jumbo squid Dosidicus gigas (415–875 mm mantle length (ML)) of different stages of maturity from the Gulf of California and Nicaragua were analysed. Oocyte development is asynchronous during female ontogenesis, with predominance (>85–90%) of small protoplasmic oocytes 0.1–0.2 mm in diameter for all stages of female maturity. Potential fecundity (PF) is determined at late immature stage II with average values around 18–21 million oocytes. The maximum PF estimated, 32 million oocytes, is so far the largest recorded for any cephalopod. PF is closely related to female size. Nicaraguan females, of smaller size (415–720 mm ML), show lower fecundity (5–15 million oocytes). Eggs were analysed in oviducts of mature females (540–875 mm ML), 7 from the Gulf of California and three females from Nicaragua. Eggs measured 0.9 × 1.1 mm in diameter and weighed 0.45 mg on average. The oviducts of the largest female (875 mm ML) held 1.2 million eggs, representing 4.6% of PF and no more than 14% of all vitelline oocyte stock of that squid. Variability in oviduct filling is very high and unrelated to ovary weight. However, a strong correlation was found between oviduct fullness and nidamental glands development. These observations suggest that spawning is extended and intermittent. A female spawns no less than half of the initial PF, and the minimal number of spawning activity events (egg batches) is roughly estimated at 8–12. During this terminal spawning stage females continue actively feeding and grow between egg-mass laying periods.