An experiment was conducted to investigate the influence of manganese (Mn) oxide added to mixed feeds on the performance of broiler chickens and Mn retention in the tibia bone. Six hundred broiler chickens were divided into 5 groups, and fed on maize-based diets without supplemental Mn (group I) or with a supplement of 50 mg/kg Mn as sulphate (group II) or 3 different feed grade manganese oxides (groups III, IV, V). The greatest mean body weight of 2146 g was found in group II. Mean body weights in the other groups were from 4.3 to 2.7% lower (P < 0.05). Body weights and feed conversion rates of chickens fed diets supplemented with Mn oxides were similar to control birds fed a diet without supplemental Mn. Chickens of group II utilized mixed feeds most effectively (P < 0.01). Addition of Mn to diets at a level of 50 mg/kg as sulphate or oxides resulted in a tendency to increase the Mn concentration in the tibia of broiler chickens. Mn availability from the investigated manganese oxides ranged from 61 to 74% and was lower than that from the sulphate, taken as 100%.