Ewes are normally shorn once yearly, usually in early summer, to maintain sheep welfare and to minimize fly strike. Winter conditions in Ireland are characterized as relatively mild. Consequently ewes which are housed unshorn may have difficulty dissipating body heat due to the unique insulating properties of the fleece, leading to ineffective heat regulation. Results from previous studies at Athenry (Keady et al 2007, Keady and Hanrahan 2007) showed that shearing at housing increased lamb birth and weaning weights by up to 0.63 and 2.5 kg respectively. Shearing at housing may require a greater management input as ewes are normally housed in smaller groups and need to be dry prior to shearing. However, shearing in the autumn prior to mating enables the total flock to be assembled under more favourable conditions. The number of lambs weaned per ewe mated is the major factor influencing efficiency of prime lamb production (Keady and Hanrahan 2006). It is unknown if shearing prior to mating, in a temperate climate, impacts on subsequent ewe fertility and litter size whilst at the same time producing heavier lambs relative to shearing at the conventional time in early summer. The aim of this study was to evaluate the effect of the season of shearing on ewe fertility of March lambing ewes and subsequent lamb birth and weaning weights.