Postruminal infusion of glutamic acid has been shown to increase small intestinal starch digestion in cattle. Our objective was to determine response among small intestinal starch digestion in cattle provided increasing amounts of postruminal glutamic acid. Five ruminally, duodenally, and ileally cannulated steers (351 ± 11 kg BW) were fed (5.1 ± 0.06 kg DM/d) a soybean hull-based diet that contained only slight amounts of starch (0.8% DM) and placed in a 5 × 5 Latin square with 12-d periods. Cattle received (DM basis) continuous duodenal infusion of raw cornstarch (1.5 ± 0.08 kg/d), and either 0 (control), 30.9 ± 0.6, 62.4 ± 1.2, 120.4 ± 3.4 g/d glutamic acid or 407 ± 18.3 g/d casein (a positive control). Ileal and fecal nutrient flows were measured during the last 4 d of each period and CrEDTA served as an indigestible marker. Amounts of starch infused did not differ (P = 0.46). Casein increased (P = 0.05) small intestinal starch digestion. Similarly, small intestinal starch digestion increased linearly (P = 0.02) with increasing amounts of glutamic acid. Ileal flow of ethanol soluble starch tended to decrease (linear = 0.16) with greater amounts of glutamic acid, but ileal flow of ethanol soluble starch was not affected by casein (P = 0.42). Ileal flow of glucose was small (8.5 ± 3.0 g/d); however, greater glutamic acid flow tended (quadratic = 0.08) to decrease ileal glucose flow. Fecal starch flow decreased in response to casein (P = 0.01) and glutamic acid (linear = 0.04; cubic = 0.04); however, fecal flow of ethanol soluble starch and glucose were not affected by casein or glutamic acid. Postruminal starch digestion was increased by both casein (P = 0.02) and glutamic acid (linear = 0.05; cubic = 0.03). Our data indicate that small intestinal starch digestion is linearly increased by postruminal glutamic acid flow.