The objective of this study was to determine an optimum lysine to calorie ratio for 25-120 kg barrows and gilts in a commercial finishing environment. It is suggested that feed cost per kilogram of gain decreases, and reduction in biological performance and income over feed costs are rather modest when feeding lysine deficient diets early in the growerfinishing period. However, there was severe growth reduction when they were fed marginally deficient lysine diets in the late finishing period.