This experiment was conducted, with 480 chicks for a period of 5 weeks, to study the toxicity of dietary hexavalent chromium and the influences of cobalt on the chromium toxicity in the chicks, 4 levels of added hexavalent chromium (0 , 300ppm, 600ppm, and 900ppm) were added in the absence or presence of the same level of 150ppm cobalt. 3 pens of 20 chicks were assigned to each of the dietary treatments, and p$lt;0.05 was taken as the limit of statistical significance. The results obtained are as follows; 1) Chicks showed adverse effect from 300ppm of hexavalent chromium in growth rate, but from 600ppm in mortality, 2) An exaggerating tendency of the chromium toxicity, in growth rate and mortality, was shown by adding cobalt, 3) As higher the levels of hexavalent chromium were administered, an increasing tendency was shown in feed requirement, Adding cobalt increased the feed requirement at the level of 600ppm of hexavalent chromium, but didn`t modify the feed requirement from the other levels of hexavalent chromium.