Elevated rectal temperature, mucopurulent nasal discharge, mortalities and abortion of pregnant ewes were the main clinical abnormalities recorded in sheep flocks at Seedy Salem Village, Kafr Al-Sheikh Governorate, Egypt following their vaccination by the attenuated Rift Valley vaccine. Meanwhile, 45 of the farmers in the village showed variable findings suggestive for a RVF epidemic and 17 farmers died of haemorrhagic fever as reported by the World Health Organization, WHO (2003). Blood serum samples were collected from 78 humans and 86 sheep and tested for RVF antibodies. We found that, where 11 (12.94%) and 10 (19.30%) of sheep and human sera respectively were positive. The recent history of vaccination of such flocks using the attenuated RVF vaccine lead us to suggest that the used vaccine might be the source of such epidemic.