The purpose of this investigation was to determine some biological parameters of the predator, Nabis pseudoferus Rem. (Hemiptera: Nabidae), feeding on the Egyptian cotton leaf worm Spodoptera littoralis Boisd. (Lepidoptera: Noctuidae). Experiments were conducted in a climatic chamber at 25 +/- 1 degrees C and 60 +/- 5 % RH under 16:8 light:dark photoperiod. N. pseudoferus feeding on S. littoralis individuals being on cotton seedlings kept in cages (12x8x7 cm) was used for the experiments. Mortality rate was 33.33% and females laid an average of 50.92 eggs during their life time. From the constructed life table, the following parameters were obtained: the intrinsic rate of increase (r(m), 0.079 females/female/day), net reproduction rate (R-o, 31.00 females/female), mean generation time (T-o, 43.246 days), gross reproductive rates (GRR, 37.992), doubling time (T-2, 8.729) and the finite rate (lambda) of N. pseudoferus (1.083), respectively.