The results are given from trials which were designed to demonstrate the effects of feeding antibiotics and a tranquiliser to beef cattle. In Trial 1 the feeding of 80 mg. aureomycin daily produced no significant effect. In Trial 2 the feeding of neither 2·5 mg. hydroxyzine nor 80 mg. terramycin nor the two combined produced any significant effect except to depress the level of intake of dry-matter over the whole trial period. This reduction in drymatter intake did not lead to an increase in efficiency of conversion (lb. dry-matter intake per lb. live-weight gain). In trial 2 the tranquiliser tetrahydrozoline was unsuccessfully used at the beginning of the trial in an attempt to reduce the loss in live-weight suffered when the animals were tied up.