The body condition of the gilt at first mating may have a significant effect upon its lifetime reproductive performance. (Gueblez et al, 1985). Gaughan et al (1995), have recently demonstrated that gilts with low backfat thickness (9- 13mm) had fewer litters and weaned fewer piglets than gilts with medium (14-16mm) and high (>17mm) levels. The extent to which variations in both body weight and backfat thickness of gilts at first mating influence long-term reproductive efficiency has been further investigated in a commercial trial at the JSR Commercial Development Unit, Catwick. The overall objective of the trial was to assess the long-term performance of modern pig genotypes under commercial conditions.