locally isolated strain of bovine ephemeral fever virus particles from outbreak in native breed 2000-2001 was examined by electron microscope and showed bullet or cone shaped, with an average length of 140-180 nm and diameter of 45-85 nm after passage (/C) on baby mice or Verol21 and BHK21 cell line, the complete virus particles consisted of spikes, a membranous envelope and a helical nucleocapsid, This spike were easily disrupted. The harvest of BEF virus contained defective fi interfering particles. These particles were short cone-shaped forms about one - third the length of the infectious particles and similar in morphology to infectious virions . These particles interfering with virus replications. The BEF virus was affected by Storage at 4°C and -20 °C losing its infective titer]-1.1 log10 at 4°C forl8 hours and 1.6 and 1.7 log10 at -20°C for 2 months. The virus lost it's infective titer within 20 min at 56°C, and was very sensitive to ether and chloroform as it decreased 4 and 2.6 log10 when treated , respectively. The isolated BEFV was not able to agglutinate any RBCs of different species.