It has become increasingly apparent that the Japanese and Western systems of classifying dysplasia and carcinoma in the gastrointestinal tract are not the same. The implication of these differences is that in an article in a Western journal on gastrointestinal 'cancer' originating from Japan, it is often impossible to repeat the study to confirm or refute it, because of these differences in definitions. Although there is no reason why it should not be just as much of a problem if Western research is published in Japanese journals, this is currently not a major problem. The terminological differences do not mean that one is right and one wrong; they are simply different. We had an opportunity to look at these differences in detail in a series of 100 gastric biopsies. In this review, we outline these differences and indicate the similarities, differences and problems between these two systems. 'Carcinoma' is diagnosed in Japan by virtue of its structural and cytological features, but by invasion in the Western system. Adenoma does not mean a dysplastic lesion in the Japanese system (although it can) but in most cases is similar to low-grade dysplasia irrespective of the macroscopic/endoscopic appearances (hence flat and depressed adenomas in the Japanese system); however, most examples of high-grade dysplasia in the Western system, as well as some low-grade dysplasia, becomes 'cancer' in the Japanese system. Conversely, both have conceptual areas that are useful in the other's systems. Because we were ultimately able to use each other's systems, we were able to show where these systems come together and diverge. These provide hope that a common classification encompassing both systems that allows communication between both systems is feasible.