Adult male Culex tarsalis irradiated and released into large outdoor field cages at ratios (irradiated:unirradiated) of 1:1, 2:1, and 9:1 were expected to "sire" egg rafts with hatch rates (low hatch/high hatch) of 1:1, 2:1, and 9:1 based on a competitiveness value of 1.0. Male to female sex ratios were 2:1, 3:1, and 2:1, respectively, for each field cage release. The observed hatch rate ratios did not differ significantly from the expected values at each ratio, but the overall reduction in hatch was greater at higher ratios.