The dewlaps of anoles vary greatly in size, including some species that have no dewlaps at all.  The dewlap serves many purposes--including courtship, territorial interactions, species recognition, and predator deterrence--and must be an effective communicatory signal in different light environments.  We measured dewlap size in 52 species of Caribbean anoles to test a variety of hypotheses concerning the evolution of dewlap size.  Species with conspicuous body coloration or patterning tend to have relatively smaller dewlaps than do other species.  In addition, the data suggest the possibility that species in poorly lit habitats may have relatively larger dewlaps than species in brighter habitats.  By contrast, no relationship exists between relative dewlap size and structural habitat, display rate, or sexual size dimorphism.  Further, comparisons of the dewlaps of sympatric species do not support the hypothesis that differences in dewlap size aid in species recognition.