Abstract
Isospora lacazei was described from large number of passeriform birds including house sparrow (Passer domesticus). It was not certain whether all described species under this name belong to the same species. Also, two other species (Isospora passeris and Isospora passerum) were identified from P. domesticus depending on variation of oocyst measurements. During the present study, the Isospora species was reported from house sparrow (P. domesticus) in Saudi Arabia. The oocyst measurement ranges cover all the ranges of the previously described Isospora species from P. domesticus. Therefore, the present species could be identified as I. lacazei, whilst the other species being described can be considered as a junior synonym of I. lacazei.