During the period from 1982 to 1993, 1185 Shigella strains from the National Network of Diarrhoeal Laboratories were sent to the Enteric Bacteriology Laboratory of INDRE. These strains from patients of various ages with diarrhoeal illness were serologically confirmed. The frequency was as follows: S. flexneri (61.35%), S. sonnei (26%), S. dysenteriae (6.4%) and S. boydii (6.2%). S. dysenteriae 1 is an epidemiologicaly important species because it has caused diarrhoeal outbreaks on the southern border of Mexico that later spread through Central America. It must be considered that the 20 isolates obtained in 1989 were from an intentional search focused on S. dysenteriae. Authors pretend to continue with epidemiological surveillance focused on Shigella and intensify the intentional search in order to identify possible human or environmental S. dysenteriae 1 reservoires.