The binding specificity of Wisteria floribunda lectin (WFL) is not completely clear but this lectin appears to preferentially bind carbohydrate structures terminating in N-acetylgalactosamine linked α or β to the 3 or 6 position of galactose. This lectin has been used to fractionate lymphocyte populations, and although not mitogenic, elicits the production of lymphokines from murine splenocytes. Fluorescein labeled WFL has an appropriate number of fluorochromes bound to provide the optimum staining characteristics for this lectin. This conjugate is supplied essentially free of unconjugated fluorochromes. The excitation maximum is at 495 nm and the emission maximum is at 515 nm.