The majority of low grade non-Hodgkin's follicular lymphoma undergo clinical progression to intermediate and high grade lymphoma, but the molecular mechanisms involved in this transformation are not yet well understood. In this article, we describe the case of a 66 year old man with follicular non-Hodgkin's lymphoma (NHL), in whom a centroblastic leukaemic transformation led to death in six months, despite a transient period of remission. At the time of transformation, cytogenetic analysis revealed the original coexistence of t(14;18)(q32;q21) and t(8;22)(q24;q11). These results were confirmed by fluorescent in situ hybridization, while molecular analysis showed a BCL2-JH rearrangement but failed to detect a c-myc rearrangement or any additional p53 mutation. Our observations would therefore suggest other mechanisms to be involved in the transformation of follicular NHL.