Primary malignant lymphoma of the bladder is a rare tumour. In a recent literature search only 70 cases have been found since 1885. Most of these tumours were low grade B-cell non Hodgkin's lymphomas and only 20% were high grade neoplasms. This tumour usually appears in women between 20 and 85 years (median 64 yr.) of age. 20% of them have antecedents of chronic cystitic. Some authors have considered that some of the primary malignant lymphomas of the bladder arise from the mucosa-associated lymphoid tissue (MALT), therefore acting like MALT lymphomas which affect the gastrointestinal tract, the salivary glands or the thyroid. We report three additional cases of primary malignant lymphoma of the bladder, two of high grade, and discuss the histological criteria that support their MALT nature.