Fermented milk is a popular drink. Recent studies revealed that some fermented milk containing some strains of lactic acid bacteria have health-promoting effects through improvement of the intestinal microflora and modulation of the immune system. Lactobacillus casei strain Shirota (LcS) is a probiotic bacterium used in the production of fermented milk products and lactic acid bacteria preparations. LcS has been shown to modify allergen-induced immune responses in allergic rhinitis, altering fermentation patterns in the small bowel, prevention of recurrent urinary tract infections in women. Yakult®300 is a fermented milk containing at least 3x10^10 live LcS cells per 100 ml bottle. This study aimed to evaluate the effects of a fermented milk drink containing Lactobacillus casei strain Shirota on the human intestinal microflora.