Technological improvements are enabling flow cytometry to assess an increasing number of markers simultaneously. This presentation will describe the advantages and disadvantages of an eight colour diagnostic flow cytometry system. In the determination of lymphocyte subsets, the system enables each sample to be analysed in a single tube. In haematological malignancies, the eight colour system provides improved sensitivity in the assessment of small populations. For example, several B cell markers can be determined in the same tube as kappa and lambda, enabling detection of small monoclonal B cell populations, and distinction of monoclonal populations from reactive follicular hyperplasia. The eight colour system is very useful in assessing minimal residual disease. A greater number of markers can be determined when samples, such as CSF, are analysed in a single tube because of low cell numbers. There have also been improvements in work flow, and reductions in the cost of antibodies used in multiple tubes. Disadvantages include greater complexity in data analysis, more training for pathologists and laboratory staff, and custom preparation of antibody‐fluorochrome conjugates. Implementation depends on a highly skilled laboratory scientist. On balance, the improvements in diagnosis have justified the use of an eight colour system.