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A study was carried out to evaluate growth performance of Zebu cattle and their crosses with Sahiwal and Boran at the National Semi-Arid Resources Research Institute (NASARRI), Serere, Uganda. Analysis of variance based on General Linear Model of SAS 2002 was used to analyse the data. The overall means for weights at birth and weaning and pre-weaning average daily gain (ADG) were 18.36± 0.076, 100.55 ± 0.48 kg and 304 1.96 g day-1, respectively. Dry season born calves were significantly (P<0.05) superior to wet season born in both weaning weight and pre- weaning ADG. Parity had a significant (P<0.05) influence on birth weight but not for weaning weight and pre-weaning ADG. Genetic group of the calf (Zebu, Boran or Sahiwal crosses) was a significant (P<0.001) source of variation for all growth traits studied. Rankings of genetic groups for weaning weight and pre-weaning ADG were B1Sx (SxT), F1(SxT), B1(SxT)xT, B1Bx(BxT), F1(BxT) and T. Influence of year calving was significant (P<0.01) for weaning weight and pre- weaning and pre-weaning ADG but not for birth weight. Heritability estimates based on sire variance components for birth weight, weaning weight and pre-weaning ADG were 0.41, 0.02 and 0 .02, respectively. Heritability estimates based on both the dam and the sire variance components for birth weight, weaning weight and pre-weaning ADG were 0.41, 0.16 and 0.36, respectively. Based on these results it can be suggested that crosses of Boran and Sahiwal have higher potential for growth than the Zebu cattle. However, backcrossing to either Sahiwal or Boran breeds had no significant advantage over the F1crosses.