Estimates of genetic parameter for economically important traits are base for genetic evaluation, planning breeding program and selection. This study was aimed to estimate phenotypic parameters, genetic parameters and breeding values of selected growth traits of Awassi x Menz sheep in Debre Birhan sheep breeding and multiplication center. From the total pedigree data 5863, 4452 and 4324 data for birth weight (BWT), weaning weight (WWT) and pre-weaning average daily gain (PWADG) records, respectively, were used for analysis. The effect of non- genetic factors on growth performance was assessed by GLM of SAS (9.1), whereas, genetic parameters were generated by Wombat software. The Log L. test was used for selecting the best model from six models. The direct additive effect was included in all models and it was the only random effect at the first model. In the 2nd and 3rd model permanent environmental and additive maternal effect, respectively, was fitted as 2nd random effect. The 4th model was the same as the 3rd Model, but allowed for direct-maternal covariance. The 5th and 6th model included both permanent environmental and additive maternal effects with omitting and fitting, respectively, direct-maternal covariance. Based on the log L test the 6th model for BWT and WWT, and the 5th model for PWADG trait was the best fitted. The overall mean with their standard error of BWT, WWT and PWADG were 3.75 ± 0.015, 15.52±0.116 and 0.105±0.00 Kg, respectively. The corresponding estimates of direct heritability with its standard error from the best model were 0.230±0.042, 0.125±0.035 and 0.250±0.067, respectively. There was strong positive genetic correlation between BWT-WWT (95.7%) and WWT-PWADG (0.896) and moderate positive correlation BWT-PWADG (47.5±0.388, however all had low phenotypic correlation In general, growth performance of population was affected by non-genetic factors. Both additive and permanent environmental effect were important for source of variation for early growth traits. There was genetic variation with in the population. The direct genetic correlation and maternal correlation was negative and it suggested that there was genetic antagonism between direct and maternal effects. The regular and slow genetic trend over the time in this study suggested that the absence of selection with in the population. Keywords; Awassi x Menz sheep, Breeding value, Genetic parameter, Growth traits 1 Chapter 1 INTRODUCTION 1.1. Back