A total of 626 surgically resected gastric carcinomas were reviewed, and 24 cases (3.8%) of “gastric carcinoma with lymphoid stroma” were identified. The tumour cells were consistently arranged in an anastomosing trabecular or alveolar pattern and were densely infiltrated by lymphoid cells. The specimens were studied using mucin histochemistry and the indirect immunoperoxidase method to determine the histochemical properties of this form of gastric carcinoma. The tumour cells were consistently positive for concanavalin A paradoxical staining, class III and almost devoid of acidic mucins, features demonstrating preferential differentiation toward pyloric glands or pseudopyloric glands. Immunohistochemically, positive reactions for Leu M1 and lysozyme, marker substances of (pseudo)pyloric gland cells, were often observed. Carcinoembryonic antigen was positive in focal areas without (pseudo)pyloric glandular patterns. Secretory component was focally positive. HLA-DR was strongly expressed in most cancer cells and 17 tumours (71%) showed positivity for interleukin 1 (IL-1). The lymphoid stroma contained a high percentage of UCHL1-reactive T cells both within and around the cancer cell nests, while SL26-reactive B cells clustered in lymphoid follicles. A considerable number of T-lymphoid cells were also reactive for IL-1. A number of plasma cells with a predominance of IgG-type were distributed around the cancer cell nests. S-100 protein-positive dendritic cells were not identified. We speculate that the prominent lymphoid stroma including intraepithelial lymphocyte-like T cells with IL-1 receptors is possibly induced by IL-1 related mediators released from the HLA-DR-positive gastric cancer cells of the (pseudo)pyloric gland-type.