Male commercial broiler strain chickens were fed either a control diet (based on corn and soybean meal) or the control diet supplemented with cupric sulfate pentahydrate, copper oxychloride, or cupric citrate in two experiments conducted in floor pens. In Experiment 1, feeding copper at 125 mg/kg diet for 42 d significantly increased broiler growth; and the response from cupric citrate was significantly better than either cupric sulfate or copper oxychloride. In Experiment 2, the inclusion of copper from cupric citrate was reduced to 63 mg/kg and the length of the experiment was increased to 56 d. Cupric sulfate pentahydrate and copper oxychloride treatments increased weight gain by 4.9% and cupric citrate increased weight gain by 9.1%. The feed conversion ratios (grams of feed:grams of gain of live birds) in the birds fed copper were not significantly different from those fed the basal diet (P > 0.05) unless corrections were made for the weights of the dead birds; the adjusted feed conversion ratios (grams of feed:grams of gain of live birds + grams of gain of mortalities) for the copper-treated birds in Experiments 1 and 2 were 5.2 and 7.6% lower, respectively, than the ratios of birds fed the basal diets. Plasma copper levels increased in supplemented chicks by 35% in Experiment 1 and 24% in Experiment 2. Liver copper levels in both experiments were increased by 26% with copper supplementation. Mortality was not affected by dietary treatment in either experiment (P > 0.05).