A method of linear udder trait appraisal proposed for sheep has been applied to 2,015 ewes of Churra breed. The method is based on scoring four traits: udder depth, udder attachment, teat placement and teat size, on a nine point linear scale. The objectivity of the method, measured by repeatability among the three classifiers was satisfactory: heritabilities of udder depth (0.16), udder attachment (0.17), teat placement (0.24), teat size (0.18), and udder shape (0.24) were similar to those for dairy cattle, making it feasible to use data from the proposed linear system in a breeding programme to improve machine milkability of ewes. Genetic correlations between the udder traits were generally favourable. A notable exception to this was a genetic correlation between teat placement and teat size of 0.62. Vertical placement of teats was associated with larger teats. Genetic correlations between the udder shape and milk production was -0.26, and makes the simultaneous selection for the two traits difficult. Genetic evaluation to improve mechanical milking aptitude by means of four basic linear udder traits should be carried out using an animal model and including at least the fixed effects of lactation month, flock, classification round, parity number and classifier.