The effects of adding copper or methionine to low-protein practical diets for turkeys were studied in two experiments involving an initial total of 2,496 day-old tom poults. In Experiment 1, 0 or 120 ppm copper were added to diets providing about 75, 85, or 100% of the National Research Council (NRC, 1977) requirements for sulfur amino acids (SAA) as supplemented by DL-methionine. Experiment 2 involved four levels of copper (0, 60, 120, and 240 ppm) added to diets containing three levels of SAA (75, 100, or 125%, NRC, 1977). Sixty ppm of copper improved 8-week body weight, while the effects of 120 and 240 ppm copper were growth depressing but not beyond 8 weeks of age. Increasing the methionine content of the diets to the 100% level for SAA (1977) consistently improved weight gain of younger birds. The improved body weight from methionine additions for the older turkeys (16 to 24 weeks) however, was significant only in Experiment 1. Copper did not influence the methionine requirement in these experiments.