Fecal samples from 11 colubrid snakes, representing 10 species, collected in Ecuador during October 1994 were examined for coccidian parasites. Feces of 4 individuals, representing 4 host species, contained coccidian oocysts. Three species of Eimeria and 2 species of Isospora were observed and are described here as new. Oocysts of both Eimeria and Isospora were found in the feces of a slug-eating snake, Dipsas vermiculata. Sporulated oocysts of the Eimeria sp. are spheroid to subspheroid, 16.7 by 16.6 μm (14–18 by 14–18 μm) and those of the Isospora sp. are spheroid and 15.0 μm (13–18 μm) in diameter. Imantodes cenchoa, the common bluntheaded treesnake, was infected with a species of Eimeria. These sporulated oocysts are ellipsoid, 23.3 by 16.2 μm (25–21 by 15–17 μm). Sporulated eimerian oocysts from Leptodeira annulata, the southern cat-eyed snake, are subspheroid, 22.5 by 18.8 μm (19–26 by 17–21 μm). Feces of a juvenile Imantodes lentiferus, the bluntheaded vine snake, contained ovoid to ellipsoid isosporan oocysts, which measured 21.6 by 15.0 μm (20–23 by 14–16 μm) when sporulated.