Calosoma sycophanta L. (Coleoptera: Carabidae), is considered an important predator of some pest species such as; Dendrolimus pini L., Lymantria dispar L., Thaumetopoea pityocampa Den. & Schiff., and T. wilkinsoni Tams in forest ecosystems. Mass production and release of this beetle to the forests has been carried out by the Forest Protection Departments in Turkey. Aim of the present study was to determine the effect of different brood stock sex ratios on oviposition of C. sycophanta under laboratory conditions. Five different brood stock sex ratio groups (male 6: female 9); 3:1 (group 1), 2:1 (group 2), 1:1 (group 3), 1:2 (group 4), and 1:3 (group 5) of C. sycophanta were tested. Adults were maintained at 2612 C, 60 +/- 10% R.H., 80-85% soil humidity and a photo period of 12:12 h. Each predator individual was provided by five pine processionary moth larvae daily. Obtained results revealed that, group 1 and 2 produced significantly more eggs than the other groups. The mean numbers of eggs after twenty-eight days were 38.5 +/- 7.3 (group 1) and 32.2 +/- 4.4 (group 2) per female. Increasing female rates in brood stock (group 4 and 5) caused less ovipositional rates than in other tested groups.