A recent phylogenetic study of the West Indian Rock Iguana genus Cyclura (Malone et al., 2000) indicated that Cyclura nubila lewisi on Grand Cayman has diverged from nominate Cyclura nubila in Cuba to a degree equal to or greater than the currently accepted distinction between Cyclura nubila and Cyclura cychlura in the Bahamas. This evidence, in combination with existing and new observations of scale characters, color pattern, geographic and reproductive isolation, and phyly, leads to the conclusion that the Grand Cayman Blue Iguana, currently Cyclura nubila lewisi, is a population lineage evolving independently from populations on neighboring islands, and, like Cyclura cychlura, is sufficiently distinct and diagnosable to be considered a species, Cyclura lewisi Grant 1940. Cyclura n. caymanensis is retained as a subspecies of the Cuban Iguana, Cyclura nubila, since it appears to be at a much earlier stage of evolutionary divergence.