The group of putative natural killer cell lymphomas, also known as NK/T cell lymphomas (nasal and nasal-type) has been characterized only in recent years. Whilst a good amount of clinical information has been gathered on this group of uncommon lymphoid neoplasms, there is little information on the cytogenetic or molecular alterations. A review of the literature shows that chromosomal abnormalities are indeed commonly found in these tumours, and aberrations involving chromosome 6q are most frequent. Other non-random abnormalities include +X, i(1q), i(7q), +8, del(13q), del(17p), i(17q), and 11q23 rearrangement. It appears that deletions of the chromosome 6 at around q21-23 region is the commonest recurrent chromosomal abnormality, and fluorescence in situ hybridisation studies have confirmed the occurrence of deletions at 6q22-23 in the CD3- CD56+ tumour cells. Search for the involved genes located in this chromosome region can potentially shed light on the molecular pathogenesis of the natural killer cell neoplasms.