Pigs were fed a freeze-dried probiotic (Bifidobacterium animalis CSCC 1941) plus a high-amylose maize starch (HAMS) and a fructooligosaccharide (FOS) separately or together. Fecal output and total and individual major short-chain fatty acid (SCFA) concentrations and excretion were higher and pH was lower with HAMS than with FOS relative to when they were fed a low-amylose maize starch (LAMS; control). Fecal bifidobacteria numbers and total excretion were equally higher during feeding of FOS or HAMS and highest with HAMS + FOS. When probiotic supplementation was stopped, bifidobacteria numbers declined rapidly when they were fed LAMS, more slowly with FOS or HAMS, and were maintained with HAMS + FOS. The data confirm that both HAMS and FOS are prebiotics and suggest that they act through different mechanisms and that they are most effective in combination. However only HAMS raises fecal SCFA.