Disclosed are compositions comprising viral vectors derived from the paramyxovirus, simian virus 5 (SV5). The SV5 vectors of the present invention are designed so that the HN protein that binds to sialic acid is not expressed, and in certain embodiments a foreign membrane bound protein is expressed on the viral surface that targets the virus to particular cells or tissues. The vector then is able to deliver a toxin or cytotoxic agent to the target cell. Also disclosed are nucleic acid segments useful as viral genomes and methods of producing viral vectors.