A total of 24,179 female Phlebotomus flies collected in suburban Cairo, Egypt, were examined for phlebotomus fever virus. Virus was recovered from 4 of 59 sandfly pools tested; one pool of Phlebotomus papatasi and 3 pools of unindentified Phlebotomus, presumably consisting solely of P. papatasi, yielded virus. All four isolates were identified by complement-fixation tests as the Sicilian type of virus. Wild-caught engorged P. papatasi flies were shown to contain substances which neutralize the Sicilian type of phlebotomus fever virus. Failure to demonstrate similar activity in laboratory-reared sandflies suggests that the active principle is antibody contained in ingested human blood.