The major part of the population of Ouagadougou, Burkina Faso, have their breakfast, dinner and lunch in street food shops. The characteristics of street food vendors are indicated. It appeared clearly that women play a major part (75%) in street food sale. Vendors have only a slight knowledge of food processing and of hygienic practices. There is a high proportion (about 50%) of people among them. This dietary habit has some negative aspects on the consumers' health. Ours studies clearly showed that hygienic practices during sales operations are not respected by all categories of vendors of food products. Also, it was observed that street food vendors sometimes sit close to the waste water drainage system and solid wastes. Sometimes, the food is not covered and it is manipulated by consumers in areas infested by flies and others insects. The water used to wash the materials is of poor quality. The second aspects of our studies showed that, in most cases, when the safety and hygienic practices were not respected, the food became a true microorganism culture medium under tropical climatic conditions. A table reports microbial analysis and contamination rates of some important street foods consumed in Ouagadougou. In general these results showed the failure of microbial quality of some food which is not preheated (milk product, fruit juice, vegetable, fruit) and in the case of food which is not reheated after a long time of exposition (dry meat and meat on sticks). The presence of Salmonella and Shigella species in some food represents a serious danger for consumers. These aspects were observed with most street food vendors. It probably makes street food the source of most diseases caused by bacteria and other microorganisms.