Soymilk fermented with Lactobacillus plantarum HOKKAIDO was examined for its effect on fecal properties and growth of useful intestinal bacteria in sixteen healthy volunteers (ages 24-83 years). Fecal properties were not affected by the intake of the fermented soymilk. Subjects who had a low number of Lactobacillus (less than 1.0 x 10⁷ CFU/g, 2 subjects) or Bifidobacterium (less than 5.0 x 10⁸ CFU/g, 2 subjects) in feces showed a significant increase in viable cell numbers of these bacteria during fermented soymilk feeding. Most of the fecal Lactobacillus detected in randomly selected fecal specimens during feeding belonged to the HOKKAIDO strain. We conclude that the fermented soymilk functioned as a synbiotics.