Clinical flow cytometry is a critical tool for immune-oncology research because it enables the measurement of different cell types and their functional status. This type of flow cytometry data is critical to evaluating therapeutic effects of experimental therapies in animal models as well as assessing clinical responses. Clinical flow cytometry requires the development of validated panels, which are comprised of fluorescently labeled antibodies that bind to specific molecules on different cell subsets. Here we highlight essential considerations for the development and validation of a clinical flow cytometry panel.