Field observation revealed that the most common symptoms on naturally infected plants in Alexandria, Dakahliya, Kafr El-sheikh and El- Beheira governorates in Egypt were severe mosaic, mild mosaic, chlorosis, mottling, vein banding, blisters, malformation, fern leaf, shoe-string and/or stunting. These symptoms were suspected of being caused by Cucumber mosaic virus (CMV) and confirmed by indirect ELISA. Two samples obtained from wild tobacco and cucumber plants reacted positively with the CMV specific antiserum. Based on symptomology and disease severity on Nicotiana glutinosa and Chenopodium amaranticolor, two isolates of CMV were named CMV-wild tobacco (from Alexandria) and CMV-cucumber (from Kafr El-sheikh) and subjected to this study. Reaction of some diagnostic hosts of 11 plant species belonging to five families upon inoculation with the two isolates included different symptoms characteristic to CMV-infection, albeit those induced by CMV-wild tobacco being invariably more severe than those elicited by CMV-cucumber. Identification of virus isolates was confirmed using real time reverse transcription PCR (qRT-PCR). The test isolates demonstrated a single qRT-PCR amplification product of 500bp. The two isolates could be transmitted mechanically and easily transmitted by four aphid species in non-persistent manner. The most efficient vector was Myzus persicae followed by Aphis gossypii, Rhopalosiphum maidis and A. nerii with transmission rates of 90%, 70%, 60% and 50%, respectively, for CMV-wild tobacco and being 80%, 80%, 40% and 30%, respectively for CMV-cucumber. The two isolates could not be transmitted via Cucurbita pepo seeds derived from infected plants. However, virus infection had a great effect on seed germination.