The present study describes five patients with leukaemic non-Hodgkin's lymphoma (NHL) detected on the basis of particular morphology and cytogenetic findings. With respect to histological, immunological and cytogenetic features these NHL are closely related to mantle cell lymphoma/intermediate differentiated lymphocytic lymphoma. However, the presence of unusual large cells associated with the t(11;14)(q13;q32) translocation and numerical chromosome changes, in the near triploid or near tetraploid range, could delineate a particular subtype of mantle cell lymphoma.