1. A comparison has been made of the progenytest figures for father and son in the Friesian breed. 2. There was a significant regression of contemporary comparison of son on contemporary comparison of father (0·22) and on r.b.v. of father (16·4 lb. per unit of r.b.v.), though both figures were about one-quarter lower than expected. The observed figures were consistent with a heritability of heifer yield of 0·19. The regression of contemporary comparison of son on the average production of the herds in which his half-sibs were milked was small and not significantly different from zero. 3. For fat content, the regression of son's daughter average on father's daughter average was 0·32, in agreement with expectation. 4. A less-detailed analysis for the Ayrshire breed on the above points gave essentially similar results. 5. The possible extent of selection on the basis of progeny-test results was looked into. For yield, the selection was small, leading to a probable improvement of 1–2 gal. a year. For fat content, the probable increase was 0·01% a year. 6. A method is described for evaluating the progeny test of a son in relation to his father's own progeny-test results, which can serve as a method of combining the progeny-test figures from different bulls.