Dysenteric syndromes are relatively frequent in tropical areas, due essentially to infectious etiologies, constituted by flimsy pathogenic agents outside and possibilities of laboratory investigations little available. The authors evaluated during two years (1990-2000) the results of 399 parasitological examinations and 419 bacteriological examinations concerning dysenteric syndromes admitted to the laboratory of "Hopital Principal de Dakar". The objective of these examination is to contribute to the management of cases. The patients are divided into two groups: the first group is constituted by children less than two years old hospitalised in the pediatric services, and the second group includes all the other patients. The parasitological studies schow that parasitic etiologies are almost non existent in the first group while in the second group, they are essentially represented by Entamoeba histolytic with 19.5% of prevalence. The bacteriological studies show 42.7% of positivity rate in the first group and 19.5% in the second group with a predominance of E. coli and Shigella dysenteriae. The prevalence or pathogenic agents associations is not neglectable: they represent 8% or positive results with a predominance of amoeba-Shigella association. These results confirm the necessity of a best case management during the preanalytic phase in order to improve the scores of positivity and the particularities of hospitalised children les than two years old, to when the frequency of observed cases is high with bacteriological etiologies essentially (E. coli EPEC+, Nosocomial bacteria).