In a retrospective reclassification of 148 non-Hodgkin's lymphomas the reproducibility of the Lukes--Collins classification used was tested by comparing a joint diagnosis with that of each author separately. The cases of disagreement were usually proved to have happened within lymphoma groups with an equivalent prognosis. An exception was the relatively high disagreement rate between the subclasses of small lymphocytic and small non-cleaved lymphomas, and this represents the most important finding clinicopathologically.