SUMMARYOne-hundred-ninety-five Duroc (D), Hampshire (H), Duroc X Hampshire (DXH) and Hampshire X Duroc (HX D) boars were evaluated for reproductive performance. One-hundred-sixteen boars were castrated at approximately 225 days of age to evaluate testicular and epididymidal weights and sperm numbers. Testes from crossbred boars were 95.33 + 22.81 g heavier (P<.01) and contained 14.4I + 3.92 billion more sperm (P<.01) than those from purebred boars. Testes from Hampshire boars were 50.40 + 31.75 g heavier with 6.27 + 5.45 billion more sperm than those from Durocs. There were no significant differences between breeds for caput-corpus epididymidal measurements. Durocs had 24.55 + 12.16 billion more sperm (P<.05) in the cauda epididymis than Hampshire boars. Testes weight and testes sperm numbers were significantly correlated with caput-corpus epididymidal and cauda epididymidal sperm numbers. Correlations of testicular and epididymidal characteristics with growth rate and backfat to 100 kg were small and nonsignificant.Twenty 7.5-month to 9-month-old D, Dx H and HXD boars and 19 H boars were each mated to two Yorkshire gilts to evaluate reproductive efficiency. Conception rates were: D, 63.2%; DXH, 67.5%; HXD, 60.0%; and H, 48.6%. Number of embryos 30-days postbreeding was 10.66 + .49 and 11.25 -+ .43 (P>.10) for gilts mated to purebred and crossbred sires, respectively. Twenty-eight of 36