In June 1991 feces from 16 Anolis distichus from Barahona Province, Dominican Republic, were examined for coccidia. Lizards were found to harbor an undescribed isosporan, herein described as Isospora guarocuyai n. sp. Oocysts were subspherical, 20.2 (19.2-21.8) x 17.2 (14.9-19.2) mum, with a bilayered wall ca. 1.5 mum thick. Oocysts contained single polar granules and all contained granular debris. Sporocysts were ovoid, 13.0 (10.9-13.8) x 8.6 (6.9-9.4) mum, with Stieda and substieda bodies. A sporocyst residuum was present in the form of numerous minute globules. This is only the fourth species of Isospora to be described from iguanian lizards and the first from Hispaniola.