Enteropathogenic Escherichia coli (EPEC) is a leading cause of diarrhea in infants less than two years of age in developing countries. To induce diarrhea EPEC uses several virulence factors acting on a still unknown and mysterious mechanism. The hallmark of EPEC infection is a histological intestinal alteration known as the attaching and effacing (A/E) lesion. The bacterium attaches intimately to the enterocyte and induces assembly of cytoskeleton intracellular actin on the cellular surface. Rearrangements of the actin cytoskeleton form a pedestal-like structure where bacterium tightly cups the cells, leading to degeneration of brush border microvilli. Although the mechanism of EPEC-induced pedestal formation has been dissected in detail, the overall mechanism of diarrhea is still obscure. It is believed that EPEC-mediated secretory diarrhea is related to a) intestinal microvilli effacement, b) massive loss of intracellular ions into the intestinal milieu and c) secretion of an EPEC enterotoxin. Epidemiological studies conducted in developing countries have shown that EPEC is one of the main bacteria frequently isolated from children with diarrhea, causing high morbidity and mortality rates. The microbiological diagnosis of EPEC-induced disease is performed with analytic methodologies different from those used by the standard microbiology laboratory, the most relevant being: a) serotypification, b) the adherence assay, c) FAS test, and d) the specific detection of virulence-involved genes (bfpA and eae genes) using molecular biology techniques. The purpose of this review is to update the most recent findings regarding the molecular pathogenesis of EPEC, its epidemiology in Mexico as well as other developing countries, and also the developed methodology for the diagnosis of EPEC infection.