Vesicular stomatitis virus (VSV), an enveloped RNA virus from the Rhabdoviridae family, is released from the plasma membrane of host cells by a process called budding. The fusiogenic envelope G glycoprotein of the vesicular stomatitis virus (VSV-G) that has been used to pseudotype retrovirus and lentivirus vectors can be used alone as an efficient vehicle for gene transfer. VSV-G protein is secreted into the culture medium as sendimentable vesicles from cells transfected with a VSV-G expression plasmid in the absence of other viral components. The VSV-G vesicles in the conditioned medium can be partially purified by pelleting through sucrose cushion ultracentrifugation.