Histologically processed tissue from gastric cancers has been analyzed by flow cytometry in an attempt to correlate DNA ploidy pattern and behavior of the tumor. Of the mucosal and submucosal cancers (so-called early, all stage I in the present series), 62.7% show a diploid DNA pattern and 37.3% show a single aneuploid pattern. Of the deeply infiltrating (beyond the submucosa) cancers (stage II and III), 52.1% are single aneuploid and 47.9% are multiploid. While stage-I patients are all alive at the end of the follow-up period (6 years), in stage II and III cases Cox's regression model shows that the hazard function depends on DNA pattern: survival is negatively influenced by multiploidy. On this basis, it may be assumed that the DNA pattern is a useful prognostic indicator of gastric cancer. As expected, in Cox's regression model an even more important negative correlation exists between survival and stage: single aneuploid cases in stage II have a better prognosis than those in stage III. Instead, no correlation is found between histological cancer subtype (Laurén and WHO classifications), grade and DNA pattern.