Changes in the activity of the digestive enzymes against carboxymethylcellulose (CMC), alginate, laminarin, and fucoidan in postlarval abalone Haliotis discus hannai were measured from 7 days after settlement (Day 7) to 46 days after settlement (Day 46) every 5-10 days. Shell length (SL) and protein per individual showed a rapid increase after Day 37. Enzyme activity was not detected on Day 7 (0.52 +/- 0.01 mm SL, mean +/- standard error) bur by Day 17 (0.97 +/- 0.02 mm SL), there was detectable activity from all enzymes. This indicates that a suite of enzymes for brown algal feeding is produced even by the postlarval stage. Changes in the total activity of CMCase, alginate lyase, and laminarinase showed a pattern similar to the growth rate, with a rapid increase observed after Day 37 (1.59 +/- 0.04 mm SL). However, specific activities did not show the marked changes evident in the total activities, suggesting that the rapid increase of total activities observed after Day 37 was mainly caused by increased production of digestive enzyme with growth. Despite the negligible contents of cellulose and alginate in food of postlarvae, Days 37 and 46 postlarvae showed strong enzyme activity against these polysaccharides, suggesting that the appearance of enzyme activity during postlarval development does not require the presence of a substrate.