A graphical technique for
characterizing the light curves of RV Tauri variables is described. It is based
on three measurements which are combined into two ratios plotted one against
the other. Points that fall close together on the graph have similar light
curves and also seem to share other properties in common (e.g.: period); this
suggests that the technique might be useful for classifying members into
subclasses. The scatter of points corresponding to individual cycles can be
used as a measure of cycle regularity.