The present study investigates the lysine requirements of British United Turkey (BUT) Big 6 turkey toms from 8 to 12 and from 16 to 20 wk of age. Growth, feed conversion, and carcass quality responses to increasing dietary lysine levels were measured. From 8 to 12 wk of age (4.0 to 8.8 kg live weight), about 1.20% (4.0 g/Mcal ME) lysine in the diet was found to be adequate to obtain optimum growth and feed conversion, Nitrogen retention also tended to increase with elevated dietary lysine levels in growing turkey toms. From 16 to 20 wk of age (13.1 to 18.5 kg live weight), the highest lysine level of 0.96% (3.0 g/Mcal ME) appeared to be insufficient to maximize weight gain. It is concluded, therefore, that the dietary lysine requirement of finishing turkey toms is 0.96% lysine or higher. In addition to the growth response, a marked increase in breast meat deposition in response to dietary lysine could be observed in finishing turkeys. Increasing dietary lysine decreased intramuscular fat content and grill loss and increased the protein level in breast meat.