The 30 apple (Malus domestica Borkh.) rootstock candidates selected for cold hardiness, known as the Kentville Stock Clone (KSC), with `McIntosh' and `Delicious' as scion cultivars, were compared at 11 years of age for tree size, weight, fruit yield, and crop efficiency under field conditions. Trunk cross-section area and tree weight were highly correlated. Tree size was similar for the two cultivars in most cases and ranged in size from semidwarf to very vigorous. Cumulative yield efficiencies varied by nearly two-fold and were not correlated with tree size. The most efficient rootstocks were KSC 28, KSC 7, and KSC 6 in the semidwarf, semivigorous, and vigorous size classifications, respectively.