Recent developments in the design of flow cytometric instrumentation and advances in computerized methods of data analysis have produced flow cytometers that are compatible with the clinical laboratory setting. Because flow cytometry is impacting on virtually every area of diagnostic pathology (particularly the subspecialties of hematology, immunology, infectious disease, transplantation monitoring, neoplasia, and genetics), it is essential that pathologists develop a general understanding of flow cytometric techniques. In addition to new developments in instrumentation, simplification of laser design and advances in fluorochrome chemistry have provided several new sophisticated tools to make multiple correlative biological measurements on normal and neoplastic cells in the clinical setting. Flow cytometric analysis thus allows the pathologist to more effectively diagnose, predict prognosis, and monitor disease progression. This report reviews the basic components of flow cytometric instrumentation, the physical and biological parameters that may be assessed using flow cytometric techniques, and the multiparametric data analysis systems available for the clinical laboratory.