Four non lactating cows with rumen and duodenal T-cannules were used in the 2 × 2 Latin square experiment to study the effect of crushed or ground maize grain on ruminal fermentation and on starch outflow from the rumen, ruminal and postruminal starch digestibility. Cows were fed diets consisting of, %: forage 70, maize grain crushed or ground 27, soyabean meal 2 and Vitamix S 1, on dry matter basis. Maize treatment did not affect ruminal fermentation. Total VFA concentration was somewhat increased when the animals were fed ground maize (P>0.1). Effective starch degradability was higher (P<0.01) for ground (70.7%) than for crushed maize (65.1%). Starch passage into the duodenum was higher (P<0.01) when crushed than ground maize was fed (33.5 vs 21.2%). Postruminal digestibility of starch entering the duodenum was high for both diets (82.2 vs 85.5%; P<0.01). Apparent total GIT digestibility of starch was affected by grain processing (P<0.05).