Samples of Illex coindetii were collected with bottom trawl net at 150, 350 and 550 m depths in the Aegean Sea (Eastern Mediterranean). Sampling was carried out monthly from May 2008 to April 2009. A total of 1415 I coindetii individuals (551 males and 688 females and 176 unidentified sex) were collected. The length-weight relationship showed a negative allometry. There was a difference between the sexes in respect to length-weight relationships with females being larger and heavier than males. The smallest mature individual in the Aegean Sea, was observed to be 125 mm ML for females and 117 mm ML for males. The size-at maturity ML50 was calculated separately for males and females, and first maturation was reached at 164.8 mm ML for females and 139.3 mm ML for males. There were two peaks in GSI of females, one in spring and the other in autumn/early winter. Potential fecundities of mature females were between 46500 and 190000 and, there were 3000-7000 ripe eggs in both oviducts. Oocytes size groups distribution in ovary was bimodal at maturing, mature and advanced mature individuals so ovulation pattern was group-synchronous and reproductive strategy was supposed to be intermittent terminal spawning.