ABSTRACT.Genetic parameters for weaning weight (WW) and cow weight (CW) at different age, were estimated through a multiple trait model for the Hereford in Uruguay. Posterior mean marginal estimates were obtained using Bayesian inference with the GIBBSF90 program. WW heritability was 0.13±0.03 using a dataset of 17875. Estimated heritabilities for CW1 through CW5 were 0.39±0.07, 0.48±0.04, 0.68±0.05, 0.59±0.06 and 0.47±0.08. Genetic correlation between CW1 and CW2, CW2 and CW3, CW3 and CW4, CW4 and CW5 were 0.93±0.06, 0.69±0.09, 0.90±0.04, and 0.90±0.05 respectively. Reproductive success imposes selection, so, including WW will avoid bias. Genetic correlations between different CW were high, thus allowing for use of repeated records for genetic evaluations of MW, increasing accuracies of predicted breeding values. However, given that variances were different across ages a repeated measurement model that accounts for heterogeneous variances should be considered for genetic evaluation of mature weight.