Over 3 years, in Greyface ewes stocked at 10 or 15 per ha and mated in October (early) or November (late), lamb production at birth was related to the pattern of live-weight change of the individual ewe about mating. Based on weighings at 1·5- to 3-week intervals, ewes were grouped according to whether they were gaining (114 ewes), losing (221) or apparently maintaining weight (339) at the time of mating. Ewes losing weight produced significantly fewer lambs (1·58) than did ewes maintaining weight (1·78) while both produced significantly fewer lambs than did ewes gaining weight (1·96). Differences in lamb production between years (year 1 = 1·84, year 2 = 1·71, year 3 = 1·70) and times of mating (early = 1·82, late = 1·67) can be explained in terms of live weight at mating and the different proportions of ewes gaining, maintaining and losing weight. On the basis of earlier studies, it is suggested that the effect of direction of live-weight change operated on failure to conceive or on total loss of multiple-shed ova and was more important pre-mating than post mating.