The effect of lupin supplementation during mating on the reproduction of autumn-lambing Merino ewes was studied relative to an unsupplemented control group. A total of 158 ewes were available for lambing in 1985, 229 in 1987 and 185 in 1988. The diet of the ewes during the mating period was supplemented by 350 g grain (Lupinus angustifolius) per ewe every second day in the 1985 and 1987 lambing seasons, and by 250 g grain (Lupinus albus) daily during the 1988 season. Live mass and body condition of the ewes were unaffected by lupin supplementation relative to the control group over the entire observation period. Reproductive performance was also largely unaffected by lupin supplementation. Owing to the variable responses obtained from the present investigation, as well as those reported in the literature, it is impossible to unconditionally recommend the supplementation of lupin grain for Merino ewes on stubble lands for an increased reproduction rate.