Production differences between Merino ewes from different regions and between their progeny as determined at a central testing centre. The first Merino championships for measured production took place in 1984. A total of 31 breeders each sent 12 ewes which were three months pregnant to a central feedlot centre where the ewes were allowed to lamb and raise their offspring to weaning age. At weaning, the body mass, fold score (degree of skin wrinkling) and fibre diameter of each dam was measured. After weaning, three lambs per sex group of each breeder were selected and raised as one group to take part in the show competition. At the age of 13 months with 9,7 months of wool growth, the progeny were shorn and production measurements were taken. Dams were grouped into five groups according to area of origin. Statistically significant differences were found between dam groups for body mass, fold score and fibre diameter. However, no significant differences were found between progeny groups for body mass and fibre diameter. For fold score, one progeny group did differ significantly from the rest. These results suggest that observed differences between ewe groups from different regions were due mainly to environmental, rather than genetic differences.