A comparison of export lamb sire breeds was conducted on three properties in the Canterbury area. The purpose of this trial was to identify significant differences between, and to rank the following breeds: Coopworth, Romney, Southdown, Dorset Down, Suffolk and Poll Dorset. The traits considered were: weaning weight, birth weight, lamb survival rate and lamb productivity. Lamb productivity is defined as weight of lamb weaned per lamb born. Investigations were also conducted into the existence of sire variation within breeds and environmental effects on the former two traits. This trial was part of a larger project in which the main aim was to identify carcase quality differences between the six breeds.