A research programme was undertaken over t\vo years with the aim of increasing understanding on the effect of nutrition on ewe reproductive performance and subsequent offspring performance. The objectives of the programme were to examine the effects of plane of nutrition in early pregnancy, plane of nutrition in mid pregnancy, selenium supplementation in early and mid pregnancy and selenium supplementation throughout the productive season, on ewe and offspring performance. Performance was evaluated through a series of parameters such as fertility, prolificacy, health, embryo development, foetal growth, placental growth; lamb size at birth, lamb vigour, ewe and lamb neonatal behaviour, lamb growth rate, survival and health. Additionally, offspring from these studies were followed through after weaning for evaluation of productive performance. These experiments were carried out on three different ag~ groups: 1, 2 and > 3 year old ewes. It is concluded that for mature ewes with a marginal selenium status, selenium supplementation in early and mid pregnancy, and throughout the breeding season, positively affected measures of ewe productivity and lambs Viability. In 1 and 2 year old ewes, despite improvements in selenium status, supplementation in early and mid pregnancy had no further benefits for dams or offspring. With regard to plane of nutrition,· in adult ewes a temporary nutrient restriction in early pregnancy resulted in better lamb survival. A mild nutrient restriction in mid pregnancy tended to improve lamb neonatal behaviour and size. In 1 and 2 year old ewes, a temporary nutrient restriction in early pregnancy resulted in increased prolificacy. However, ewes and offspring were lighter at birth, presented poorer maternal behaviour and increased lamb mortality. The changes undergone to compensate for nutrient shortage or allowance in early and mid pregnancy have the potential to alter the productive performance of the offspring.