Thirty Dorset Down x (Border Leicester x Corriedale) female lambs were used to determine the effect of two fixed photoperiods (16L:8D and 8L:16D) on growth rate and body composition. Pair-feeding and controlled conditions were maintained for 91 days. Comparative slaughter procedures were used to determine changes in body composition. No significant treatment differences were detected (P > 0.05). However trends observed indicate the existence of a photoperiod effect on growth. Sheep in the long photoperiod (16L:8D) gained bodyweight slightly faster and had a higher protein content of gain.