A general idea of probiotics is given with some links to the dietary fibre. Human beings must be associated with microorganisms. The skin has hundreds grams of bacteria although, more surprisingly, the gastric tract is calculated to have I kg of microorganisms, the so-called intestinal flora. In other words, it is up to 10(11-12)/g of faeces. The most dominant genera (10(9-11)/g faeces) belonging to class I are anaerobic bacteria including Bifidobacteria. Group II includes facultative bacteria and their numbers are relatively low (10(5-8)/g faeces). The fewest bacteria such as pathogenic Clostridium perfringens and E. coli belong to class III (Mitsuoka., 1975). The small intestine possesses relatively low numbers of bacteria. However, this organ is very important because of a particular immune trap for bacteria, Peyer's patch scattering over the area. The large intestine is the largest house for the microbes. Aging is known to invite a significant reduction in Bifidobacteria, the most beneficial bacteria. Diet influences the intestinal flora balance as well. Probiotic bacteria should belong to group W. They are usually transient bacteria and proven to give beneficial effects on both digestive and immune systems. For example, Bifidobacterium breve strain Yakult improved the growth of preterm infants (Kitajima et al., 1997). Lactobacillus casei Shirota was reported to improve the constipation (Koebnick et al., 2001), and to increase natural killer cell activity. In this streamline, a habitual intake of this probiotic strain was reported to reduce the risk of bladder cancer (Aso et al., 1995, Ohashi et al., 2002). In addition there are many reports of other probiotic strains improving digestive health (Duggan et al., 2002).