I have been involved in the field of flow cytometry since 1977. My focus has been to help facilitate the use of this technology to answer biological questions. I am privileged to have been asked to contribute my cytometric expertise to a wide range of studies including the automated detection of malignant or premalignant cells, hematopoietic stem cell isolation, the study of T-cell receptor function, the detection and study of apoptotic cells,and most recently the study of effects of HIV infection in varied cell types.