The drum agglomeration of two different crushed copper ores (I and II) has been optimized using Taguchi's L16 (45) orthogonal array design to determine the optimum conditions for maximizing the average agglomerate size and minimizing the amount of fines. The effects of controllable operating factors including moisture content (ore I: 9.6-11.1%; ore II: 12.8-14%), retention time (2-4 min), drum speed (15-45% critical), drum load (ore I: 13-32%; ore II: 6-24%) and acid concentration (6.5-90 g/L) on the performance of the agglomeration process were studied. For ore I, the maximum average agglomerate size and minimum percent fines (-1 mm) occurred under the conditions: drum load (22.75%), moisture (10.35%), time (4 min), drum speed (30% critical), and acid concentration (41 g/L), whereas for ore II, the same conditions occurred under the drum load (18%), moisture (13%), time (3 min), drum speed (30% critical), and acid concentration (30 g/L). Under the conditions studied for ore I, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be drum load. For ore I, time and acid concentration had a measurable effect on maximizing average agglomerate size, whereas moisture had a statistically significant effect on minimizing the amount of fines. For ore II, the most effective parameter for maximizing average agglomerate size and minimizing the amount of fines was found to be acid concentration. Time had a measurable effect on maximizing average agglomerate size, whereas the other variables did not affect the responses significantly for ore II.