We demonstrate the feasibility of using flow cytometry (FC) to identify the Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin lymphoma (CHL). Initial flow cytometric studies of the HRS cell line L1236 demonstrated potentially useful antigens for identifying HRS cells. L1236 cells spontaneously bound normal T cells, analogous to the T-cell rosetting of HRS cells seen in tissue sections of CHL, but these interactions could be blocked by using a cocktail of unlabeled antibodies to 4 adhesion molecules. Among 27 lymph nodes involved by CHL, FC enabled HRS cells to be identified in 89%, whereas none of 29 non-CHL neoplasms or 23 reactive lymph nodes demonstrated HRS populations. Of the CHL cases, 82% demonstrated interactions between HRS cells and T cells that could be disrupted with blocking antibodies. Flow cytometric cell sorting experiments demonstrated typical HRS cytomorphologic features among the purified cells. FC may offer an alternative to immunohistochemical analysis in confirming the diagnosis of CHL in certain cases, and, through cell sorting, it provides a means of rapidly isolating pure HRS cells.