Estimates of (co)variance components were obtained for growth and efficiency traits in a multibreed synthetic beef cattle herd. Components were estimated simultaneously by fitting four alternative seven-trait models. Direct heritabilities varied according to the model fitted but were higher for pre-weaning than for post-weaning traits. Applying a model which also included maternal heritabilities, the direct-maternal covariance and the permanent environmental effect, direct heritabilities of weaning weight, weaning index, pre-weaning Kleiber ratio, pre-weaning relative growth rate, cow efficiency, post-weaning Kleiber ratio and post-weaning relative growth rate were 0.57, 0.40, 0.35, 0.71, 0.54, 0.16 and0.13, respectively. In general, maternal heritabilities varied from 0.03 for post-weaning Kleiber ratio to 0.45 for cow efficiency. Direct-maternal correlations were negative and varied from –0.31 to –0.58 for weaning weight related traits, but was –0.77 for cow efficiency.