The advent of molecular biological techniques has led to a radical improvement in the evaluation of haematological disorders and offers exciting future prospects. In particular it has led to the improved recognition of distinct clinicopathological entities defined by a combination of morphological, immunophenotypic and chromosomal features. Antibody-based techniques, namely immunophenotyping and immunocytochemical techniques, are essential to malignant haematological diagnosis. More novel is the diagnostic use of antibodies against novel fusion proteins, for example in AML, M3 and anaplastic lymphoma. PCR-based techniques allow the identification of genetic mutations and translocations including such common translocations as t(14;18), t(9;22), inv 16 and t(8;21). Fish-based techniques are greatly improving the ability to detect genetic abnormalities including those conditions with low cell proliferation and current research-based techniques include the combination of FISH with cell surface markers (FICTION), FIBRE FISH and Comparative Genomic Hybridization. Molecular techniques are essential in monitoring residual disease which is best illustrated in CML. The development of real-time automated PCR offers exciting prospects in this field. The increasing number of tests, the need for an integrated approach to diagnosis and the need for cost effectiveness indicate that such services should be provided by a specialized haematology laboratory.