Effects of maternal heterosis were estimated from preweaning and weaning data on 178 three-breed cross progeny of straight Hereford, Angus and Charolais heifers (beef) and contemporary reciprocal cross heifers. In addition, 27 three-breed cross calves produced by beef x Brown swiss females were used for a comparison of beef x beef with beff x Brown Swiss crossbred dams. Statistical analyses were performed with and without the data from the 27 beef x Brown Swiss calves. Only first-calf records, obtained from 1965 through 1967, were used to evaluate maternal qualities of straightbred and crossbred dams. Breed of sire of sow was a source of variation (P less than .01) in all progeny traits, and breed of dam of cow was a source of variation (P less than .05 to P less than .01) in all of these traits except birth weight. Interaction effects of breed of sire of cow x breed of dam of cow were consistenetly nonsignificant. Estimated maternal heterosis percentages were 1.4, 1.0, 1.1 and .4 (.02 of one grade) for birth weight, average daily gain from birth to weaning, 205-day weaning weight and weaning conformation score of progeny, respectively. Comparison of beef x Brown Swiss dams with beef cross dams showed that beef x Brown Swiss dams had calves with higher average birth weight, higher preweaning average daily gain, higher average 205-day weaning weight and higher average weaning score (P less than .05 to P less than .01).