Animal studies have shown conclusively that feeding of resistant starch (RS) increases production of large bowel total short-chain fatty acids (SCFAs). However, fermentation products of RS may be affected considerably by other dietary ingredients. In rats fed a 20% high-amylose cornstarch (HAS) with casein as the sole protein source, greater cecal SCFAs production was observed compared with that in rats fed a regular cornstarch diet. However, with this diet, the cecal succinate production was also very high. In contrast, when rice or potato protein with lower digestibility was used in place of casein, cecal succinate production decreased with a concomitant increase in butyrate. These observations suggest that nondigested protein, namely resistant protein, might play a role in correcting an imbalance in the ratio of carbohydrate and nitrogen as fermentative substrates for cecal bacteria and in promoting butyrate production. Epidemiological and biochemical data indicate a possible linkage between the fermentation products of starch (butyrate in particular) and the prevention of colorectal cancer as well as ulcerative colits. Accordingly, a fermentation strategy of RS favoring SCFA production should be established to elucidate the potentially beneficial effects of SCFAs on large bowel physiology.