Seven of 12 lacertid lizards Acanthodactylus boskianus (Daiidin, 1802), passed oocysts of an Isospora species. Comparison with other species of the genus Isospora Schneider, 1881 indicated that found coccidium represented a new species, for which the name /. abdallahi is proposed. Sporulated oocysts of /. abdallahi are spherical or subspherical, 25.8 (24.5-29.0) x 23.9 (23.0-25.5) pm, shape index (length/width) being 1.07 (1.00-1.16), with a smooth, bilayered oocyst wall that is slightly yellowish, about 2 pm thick. Micropyle, oocyst residuum and polar granule are absent. Sporocysts are ovoidal, 15.4 (14.0-16.0 x 9.4 (9.0-10.0) pm, with smooth and colorless sporocyst wall, shape index 1.6 (1.5-1.8). Stieda body is dome-like, substieda body spherical to subspherical. Sporocyst residuum is composed of numerous granules of different size, scattered among sporozoites. Most oocysts are passed unsporulated; sporulation was completed within 12 h at 25'C. Endogenous development occurs inside nuclei of enterocytes in the small intestine.