The diarrhoea diseases are priority health problems in all countries of the Third World. The number of the cases of diarrhoea and other intestinal infections have very high morbi-mortality rate in mexican childhood. There are many factors that affect these pathologies, those related to social, economic and cultural aspects seem to be the most important. Although the intestinal viruses are frequent, the enteritis produced by bacteria are more severe and acute. There area also parasites that yield the chronic type disease. In this paper, the most frequent parasites and enteropathogenic bacteria infecting children below 15 years old, either hospitalized or being outpatients from the Hospital de Zona No. 29 del IMSS in México City, were studied. The data obtained were related to the socioeconomic level. A total of 415 stool samples were collected from newborn to 14 years old children over a period of nine months. The samples were classified according to the ages, schooling and number of persons who slept with the child in the same bedroom. The samples were examined by a centrifugal concentration technique and by cultivation. The group of children up to five years old were found to be the most infected by bacteria, while children from 10 to 14 years old were by parasites. Those children whose parents either have not finished the elementary school or can not read and write were the most parasitized (40%), these children were also found to be most infected, as the number of persons who slept in the same bedroom increased, the number of infections per children either by bacteria or parasites, also increased.(ABSTRACT TRUNCATED AT 250 WORDS)