Hepatitis C virus (HCV), dengue virus (DENV) and Japanese encephalitis virus (JEV) belong to the family Flaviviridae. Their viral particles have the envelope composed of viral proteins and a lipid bilayer acquired from budding through the endoplasmic reticulum (ER). The phospholipid content of the ER membrane differs from that of the plasma membrane (PM). The phospholipase A(2) (PLA(2)) superfamily consists of a large number of members that specifically catalyse the hydrolysis of phospholipids at a particular position. Here we show that the CM-II isoform of secreted PLA(2) obtained from Naja mossambica mossambica snake venom (CM-II-sPLA(2)) possesses potent virucidal (neutralising) activity against HCV, DENV and JEV, with 50% inhibitory concentrations (IC50) of 0.036, 0.31 and 1.34 ng/ ml, respectively. In contrast, the IC50 values of CM-II-sPLA(2) against viruses that bud through the PM (Sindbis virus, influenza virus and Sendai virus) or trans-Golgi network (TGN) (herpes simplex virus) were > 10,000 ng/ml. Moreover, the 50% cytotoxic (CC50) and haemolytic (HC50) concentrations of CMII- sPLA(2) were > 10,000 ng/ml, implying that CM-II-sPLA(2) did not significantly damage the PM. These results suggest that CM-II-sPLA(2) and its derivatives are good candidates for the development of broadspectrum antiviral drugs that target viral envelope lipid bilayers derived from the ER membrane.