On May 6, 1995, CDC was notified by health authorities and the U.S. Embassy in Zaire of an outbreak of viral hemorrhagic fever (VHF)-like illness in Kikwit, Zaire (1995 population: 400,000), a city located 240 miles east of Kinshasa. The World Health Organization and CDC were invited by the Government of Zaire to participate in an investigation of the outbreak. This report summarizes preliminary findings from this ongoing investigation.