A parasitological survey was carried out on 145 dogs (125 stray dogs from different localities in Assiut Governorate and 20 foreign breed Shephered dogs in the security unit at Assiut city) to estimate the prevalence of different blood parasites during the period from March 2009 till February 2010. Out of 145 examined dogs 95 (65.51%) were infected with one or more parasitic species, 21 (14.48%) were positive for microfilariae, 34 (23.44%) with Babesia canis and 40 (27.58%) with Hepatozoon canis. The infection rate of stray dogs with different blood parasites was 72% while in foreign breed dogs was 25% (statistically highly significant). Mixed infection by more than one blood parasite was detected in 19 dogs. Two typesof microfilariae were detected in examined animals: Dirofilaria immitis and Dirofilaria repens and their infection rate in stray dogs was 3.2% and 13.6% respectively. No microfilariae were detected in the blood films of foreign breed ones. Four methods were used in this study for the diagnosis of microfilariae: direct wet method, thick blood smears, capillary sedimentation technique and modified Knott's method. The modified Knott's test was the most reliable test, its sensitivity was 66.66%. The present work cleared that the incidence of infection of dogs with different blood parasites increased with age in both breeds. The highest rate of infection with different blood parasites was recorded during Summer (95.5%) and Spring (78.6%) while the lowest rate in Winter (25%).Seasonal variations were found statistically highly significant and this may be due to correlation between the infestation rate and the flourishing of the insect population and tick infestation during this period of the year.