Examination of 89 egg masses of Sepietta oweniana collected in the Catalan Sea (western Mediterranean) showed that 15.8% of them were composed of eggs at different developmental stages laid in more than one spawning bout; 6.7% of them were polyspecific and contained eggs of other sepioline species in addition to S. oweniana. The egg mass size, or number of eggs per egg mass, does not necessarily correspond to the spawning batch size, i.e. the number of eggs laid by a female in one spawning event. Furthermore the egg mass size appears to vary depending on the season.