Early blight disease is one of the most important fungal diseases of potato. A survey of early blight disease caused by Alternaria solani was carried out in different selected locations represent different soil types and different irrigation systems in Behira, El-Sharkia, New Valley, Menoufia and Gharbiya governorates, Egypt. The pathogenicity of different isolates of the A. solani (A1-A5) was carried out on the commercially susceptible grown potato cultivar Herms. Percentage of disease incidence (PDI) and percentage of disease severity (PDS) were recorded. Results revealed that percentage of disease incidence and disease severity varies among the surveyed locations. The highest disease incidence value was recorded 98,96,98,98 and 89% respectively in Behira, El-Sharkia, New Valley, Menoufia and Gharbiya governorates. while the highest disease Severity was recorded 57.2,42.8,40.8,38.8 and 37.4% respectively in Behira, El-Sharkia, New Valley, Menoufia and Gharbiya governorates. Alternaria solani isolates A3 and A1 were the most destructive isolates. Results indicate that selected potato cultivars showed different susceptibility to early blight and the most susceptible cultivar was Herms.