The objective of this study was to elucidate the basis for the difference in sperm production of broiler breeders. Nine sexually mature Hubbard broiler breeder males, 35 weeks of age, were trained for two weeks for semen collection on alternate days by abdominal massage technique. Following the training, the breeder males were collected daily for five successive days. The males were then classified as low or high sperm producers. The mean body weights of individual males were also recorded on the basis of body weight at the start and end of the experiment. Immediately after last collection the males were slaughtered and testes biometry was determined. Daily sperm output of individual males varied from $0.21{ imes}10^9;to;2.64{ imes}10^9$ sperm. The daily sperm production of low sperm producer males was lower ($0.47{pm}0.13;vs.;2.06{pm}0.20{ imes}10^9$; P<0.05) than high sperm producer males. Testes weight of low sperm producer males was lower ($6.32{pm}1.6;vs.;20.33{pm}4.76;gm$; P<0.05) than high sperm producer males. Moreover the testis weight of high sperm producer males was 3.22 times higher than low sperm producer males. The average body weight of high sperm producer males was higher ($4,389{pm}116.3;vs.;3,960{pm}131.77;gm$; P>0.05) than low sperm producer males. The correlation coefficients indicate significantly positive correlation of body weight (P<0.05) and testes weight (P<0.01) on semen volume, sperm concentration and daily sperm production.