The pathogenetic relationship of gastric adenoma to carcinoma remains unsettled, partly due to the difficulty in discriminating between the atypical tubules of adenoma and those of adenocarcinoma. Although it has been said that this discrimination should depend not only on cellular changes but also on disorganization of glands, the latter has not been described in accurate morphological terms. In view of this, gastrectomy specimens from three patients with tubular adenoma were submitted to graphic reconstruction of atypical glands from serial sections, and were compared with well differentiated adenocarcinoma and metaplastic mucosa. Reconstruction disclosed that in adenoma, unlike in metaplastic mucosa, atypical tubules had multiple connections with adjacent ones, forming a network. At some sites of anastomosis the lumen was also connected. Though this pattern was similar to that of well differentiated adenocarcinoma, the meshes of the network were much more coarse than in the latter, showing that adenoma was a mere miniature of adenocarcinoma. The porous structure, the commonest architecture of adenocarcinoma, was never found in adenoma. There were in addition giant glands with complicated branching which, together with microcysts forming at mucosal bottom, caused convolution and twisting of tubules, producing those abnormal patterns in section on which too much stress is placed.