Broilers were grown to eight weeks of age at three experiment station locations to evaluate the influence of roxarsone and zinc bacitracin in the presence of aklomide. Dietary treatments consisted of a 4 x 4 factorial design in which levels of 0, 25, 50 or 75 p.p.m. of roxarsone were fed with 0, 15, 30 or 60 g./ton of zinc bacitracin. All treatment groups received 0.025% aklomide.Eight-week data indicated that zinc bacitracin alone produced no growth or feed efficiency response at any level of supplementation. Birds receiving roxarsone had significantly higher body weights at eight weeks of age than did birds receiving the control diet. The three levels of roxarsone produced statistically equivalent body weights.A level of 75 p.p.m. roxarsone in the presence of aklomide provided a significant improvement in feed efficiency over that seen for birds receiving either 50 p.p.m. of roxarsone or the unsupplemented control diet. Statistical evaluations indicated that the inclusion of roxarsone and zinc bacitracin in the presence of aklomide did not produce any body weight or feed efficiency interaction. The rate of mortality was not significantly influenced by any of the dietary treatments.