Karyotype analysis is now a routine procedure in the clinical evaluation of leukaemia because of its value in diagnosis and prognosis. This is not yet so for lymphoma because the relative paucity of data available has prevented an evaluation of its usefulness. We therefore karyotyped 30 unselected cases of non-Hodgkin's lymphoma and six controls with reactive hyperplasia. All cases were karyotyped 'blind' to diagnosis; all were classified by immunohistopathology and 29 were analysed before treatment. This is one of the four largest cytogenetic studies to be reported of untreated, immunotyped patients with non-Hodgkin's lymphoma. Chromosome abnormalities were observed in 29/30 tumour samples. The only rearrangement observed more than once was the 14;18 translocation. The combined results of this study and others indicate that while there are no unique associations between histological sub-types and chromosome rearrangements in untreated non-Hodgkin's lymphoma patients, some partial specificity does exist.