The general aspects of maternal effects on production traits have been revised, and particularly its incidence on weaning weight in beef cattle. The involved factors, the genetic models and the resemblance between relatives for maternally influenced traits are described. Moreover, the implications of the presence of maternal effects on selection are analyzed. The study of maternal effects on weaning weight of calves was initially carried out by means of experimental trials. Later on, numerous analyses carried out on field data have contributed estimates of direct and maternal (co)variance components of weaning weight in different beef cattle breeds. A critical review of some of these studies is done by discussing the results and also the methods and the implied assumptions in the analyses. Finally, an evaluation of the accuracy of the estimates of genetic parameters in presence of maternal effects is performed. The consequences of assuming simplified models and the existence of (co)variation factors systematically ignored, such as the environmental covariance between direct and maternal effects demonstrated in some experimental studies, are also discussed.