Reptiles of different taxonomic groups from different geographical regions all over the world were found to be naturally infected with a widely distributed rang of parasites. These parasites can be divided into endoparasites and ectoparasites . Endoparasites include Protozoa, and many helminthes. Protozoa are the most dangerous group that probably causes various diseases in reptiles, even moderate infection of these organisms in small reptiles may cause fatal diseases.The present study aimed to survey some of the parasitic protozoans and metazoans infecting many species of reptiles collected from some deserts in Egypt.This is followed by a detailed description of the recovered parasites by means of light and scanning electron microscopy. Also, the present investigation was undertaken to elucidate the whole life cycle of the haemogregarine infecting the viper Cerastes cerastes and to examine the validity of Haemogregarina as the proper genus for the species described herein.