Pseudolymphomas of the stomach are frequently associated with chronic peptic ulcer. Out of the 11 cases studied, there were characteristic pathohistological signs of chronic ulceration in eight and suspicion of chronic ulcer in three. Thus it seems that pseudolymphomas frequently represent an exaggerated lymphocytic reaction to chronic ulcer. The pseudolymphomatous reaction is essentially a follicular hyperplasia with the gradual development of progressively transformed germinal centres. These large nodular structures are usually found in the submucosa and, at first inspection, the transformed follicle can easily be mistaken for a possibly malignant diffuse lymphomatous lesion. However, once the existence of the condition is realized, its recognition by the pathologist should be easy. A heavy plasma cell infiltration of polytypic immunoglobulin type associated with progressively transformed germinal centres might be a consequence of long-standing antigenic stimulation.