1. The effect of including lupin meal (Lupinus angustifolius), with or without rapeseed meal, in computer-formulated, least-cost diets for broilers has, been determined.2. In the first experiment the diets contained 0, 8 (with and without supplementary methionine, lysine, or methionine and lysine) or 16% lupin meal: addition of the lupin meal required a concomitant addition of 5 % rapeseed meal (by computer selection).3. The diets were fed from 38 to 65 d and did not affect live-weight but the efficiency of food utilisation was significantly worse on the 16 % lupin, 5% rapeseed meal diet than it was on the control diet.4. The second experiment was designed as a 2 x 4 factorial to separate any effect due to rapeseed meal from that due to lupin meal, the treatments, which were applied from 1 to 62 d, being 0, 8, 16 and 24% lupin meal with and without 5 % rapeseed meal.5. Birds gained more rapidly in the second experiment on diets containing 16 or 24% lupin meal whereas live-weight was depressed when 5% rapeseed meal was included in the diets containing 0 or 8% lupin.6. The 16 and 24% lupin treatments also had added dietary fat from 6 to 9 weeks of age and this may have ameliorated the adverse effect of rapeseed meal.7. Up to 16% lupin meal and 5% rapeseed meal had no detectable effect on the colour, appearance, flavour or texture of roasted chicken meat when evaluated by a trained taste panel.