The last decade has been very exciting for cancer cytogeneticists. At the start of the decade, the role of cytogenetics in clinical medicine was still unclear. Many felt that such investigations were largely of academic interest. Today, cytogenetic investigations are considered essential in many cancers, where they contribute in diagnosis, staging, choice of therapeutic protocol, and monitoring of the effects of therapy. The number of primary chromosome changes in human cancer exceeds 100, and while the majority of these changes are associated with haematological malignancies, the contribution from the solid tumours is now growing rapidly. Closer ties between scientists and physicians involved in laboratory and clinical medicine have resulted in the emergence of many well-defined cytogenetic-clinicopathological entities. With the advances in molecular biology that characterized the 1980s came the disappearance of all scepticism about the critical role played by chromosome change in oncogenesis. To date, we have learned more about the details of cancer biology in chronic myeloid leukaemia and the lymphoid malignancies through the molecular dissection of primary chromosome changes than through any other approach. Further studies will, no doubt, lead us to an understanding of the molecular basis of many of the primary and secondary chromosome changes that are non-randomly acquired in human cancer.