Sixteen crosses from two strains of White Cornish and White Plymouth Rock were reared seperately on floors and abdominal fat was measured every two weeks interval from two weeks to twelve weeks of age. The abdominal fat weights surgically removed were slightly heavier in female than male. Estimates of general combining ability variances of body weight showed significant at all weeks of age in both sexes but those of abdominal fat weight were significant at 2, 8, 10 and 12 weeks of age in female and 2, 6 and 12 weeks of age in male. In percentage of abdominal fat to body weight, the significant differences were observed at 10 and 12 weeks of age only in female. The specific combining ability variances were significant at 4, 6, 10 and 12 weeks of age in female and 4, 8 and 12 weeks of age in male in body weight. In abdominal fat weight, there were significant differences at 4, 8, 10 and 12 weeks of age in female but no significant differences in male. The specific combining ability variances of percentage of abdominal fat to body weight showed significant differences at 4 and 8 weeks of age in female but no significant difference in male.