This is a retrospective study of 163 patients with Hodgkin disease and 364 patients with other lymphomas who were admitted to one Cancer Hospital (1940--1971). All the histological slides were reviewed and reclassified by one pathologist. In patients who had multiple and sequential biopsies (16 with Hodgkin disease and 97 with non-Hodgkin lymphomas), the histological subtypes remained the same in over 60% of the cases. When changes did occur, the neoplasms progressed toward histologically more malignant forms.