Some reproductive properties of Sepia officinalis from the Bay of Izmir, Aegean Sea are re-ported in this study. A total of 333 specimens, of which 81 females, 248 males and 4 immature animals were collected during monthly samplings from November 2006 to November 2007. The mantle length of all sampled specimens varied between 5.5 and 22.4 cm with an average of 11.59 ±0.16 cm. The annual sex ratio (females:males) was 1:3.1. The monthly gonadosomatic index (GSI) results indicated that the reproductive period of S. officinalis ranged from March to October, with a maximal GSI of 5.64 in May for females and from December to February and April, with a maximal GSI of 2.32 in April for males. Total number of oocytes varied from 49 to 828 with an average of 261 ±27 per specimen. The mean diameter of the oocytes extracted from 49 females was 5.21 ±0.03 mm and ranged from 1.91 mm to 9.44 mm. There were weak correlations between the fecundity of the females and both mantle length (R2=0.31) and body weight (R2=0.31).