The use of three-color analysis to detect minimal disease in CLL. CLL cells have been diluted to 1% in normal peripheral blood. (A) Plot of CD5 versus CD20 is used to gate dual-positive cells with weak CD20 in the left sided histogram. These gated cells are then plotted on the right-sided histograms for both CD20 versus κ and CD20 versus λ, showing clonality with a12:1 ratio of κ to λ for the dual CD5, CD20⁺ cells.