In malignant non-Hodgkin lymphomas (NHL), cytogenetic analysis may provide prognostic information including prediction of histologic evolution and responsiveness to therapy. In this study, we correlate clinical data and chromosomal aberrations in 70 adult patients with newly diagnosed NHL followed for a median of 20 months. Clonal aberrations were detected in 68/70 patients (97%). Besides t(2;5)(p23;q35), observed exclusively in three patients with anaplastic large cell lymphoma, Ki-1 positive, none of the characteristic aberrations observed was specific for a given histological subtype. Aberrations of chromosome 7 (n = 21) occurred in all histological subtypes together with aberrations of chromosome 3 and of the short arm of chromosome 17. They were clinically associated with a high serum lactate dehydrogenase level (LDH) and a trend to short survival. Anomalies of the long arm of chromosome 13 (n = 10) were found in patients with high grade B-cell lymphomas and bulky disease. In t(14;18)(q32;q21) bearing lymphomas (n = 27), distinct patterns of additional aberrations were observed in low grade and high grade lymphomas: trisomy 3 and trisomy 18 occurred concomitantly in high grade lymphomas (n = 6, p < 0.001) as well as aberrations of 1q, 5q, 6q and +der (18)(q21). In conclusion, cytogenetic analysis provides information about the complexity of genetic changes in NHL. These changes act not only as indicators of disease activity, but influence clinical outcome as demonstrated by their stringent correlation to the International Index and might reveal more general rules of tumor growth and spreading.