The development of more reliable diagnostic methods has undoubtedly contributed to a better knowledge of the epidemiology and role of Helicobacter pylori (Hp) in the physiopathology of upper digestive tract diseases. Non abrasive and abrasive diagnostic methods have been used; among the latter, the exfoliating of abrasive cytology has been very popular during the last years. This fact motivated us to do this investigation. A descriptive-prospective study was developed in which the sample was composed by 235 patients of both sexes. The patients underwent gastro-duodenoscopy on account of dyspeptic symptoms and in order to determine the presence of Hp and its association with endoscopically diagnosed gastritis, with or without duodeno-gastric reflux, using the SYDNEY classification system. The frequency of Hp was assessed and the density of this microorganism was correlated with the hystological type of chronic gastritis following the above-mentioned classification. As a method of diagnosis of this disease, cytology showed a sensibility of 72% a specificity of 100% and an efficiency of 77% compared with histology, that was considered the "golden test". It was histologically proved that there exists a close relationship between chronic gastritis and the presence of Hp in the gastric antrum and that when the density of the bacterial population increases, the severity of chronic gastritis increases too. This germ may show up in histologically normal mucose, being able to provoke dyspeptic symptoms and colonizing the gastric antrum independently of the presence of duodeno-gastric reflux.