To study the most important epidemiologic features of shigellosis and the application of colicinotyping as an epidemiologic marker for Shigella sonnei. A total of 44.818 stoll-cultures were performed. We classify, using colicinotyping, 156 Shigella sonnei strains isolated from different patients. The incidence of Shigellosis in our media is low (1.08% of all stool-cultures). It is more frequent in pediatric population and increases on late summer and fall. We had been able to show an increasing incidence, with an hyperendemic situation during a three-years period (1981-1983). Shigella sonnei is the most prevalent species (86% of cases), followed by S. boydii (7.3%) and S. flexneri (5.9%). All S. sonnei strains epidemiologically related showed the same colicinotype. Only two strains were not typable and we identified 9 different colicinotypes, being type 13 (30.8%), type 8 (18.6%), type 6 (17.3%) and type 12 (11.54%) the more frequent types. Colicinotype 8 was the more prevalent between 1978-1979. Type 13 was predominant between 1981 and 1985. During 1987 and 1989, at the same time that incidence had risen, types 6 and 12 were prevalent. The total number of different colicinotypes identified during a single year is never greater than five. Colicinotyping of S. sonnei is a simple typing method that gives enough useful epidemiologic information, discriminative and reproducible. Although there are changes of circulating types incidence and the prevalen colicinotype colud vary from one year to another, during longer periods of time there is a reduced number of alternating colicinotypes, which sets up a situation that could be further classified as endemic.