Green iguanas (I. iguana) and American crocodiles (C. acutus) nest in association on Slothia, a small island in Gatun Lake, Panama. In the 3 nesting seasons observed on Slothia, a crocodile remained near her nest and frequently charged the nesting iguanas. The crocodile emerged from the lake significantly more often when iguanas were present in the nest clearing. The crocodile seized an iguana on 12 occasions; 5 iguanas were eaten, 5 escaped, and the fate of 2 was unknown. In addition to the charges and captures, the crocodile''s mere presence in the nest clearing interfered with iguana nesting activity. The iguanas disturbed the crocodile nest and dug up crocodile eggs. The crocodile''s behavior involved nest defense and predatory behavior, although the exact motivational sequence is still unclear. Crocodiles and iguanas share nest sites in several other locations near Slothia. Similar nest site requirements and common nesting seasons bring the two species together.