Abstract: The preparation and use of novel lentiviral SiVagm-derived vectors for gene transfer and in particular a method of preparation of the lentiviral vectors containing capsid particles of the simian immunodeficiency virus SIVagm and envelope proteins of SIVagm and other retroviruses such as the human immunodeficiency viruses (HIV), other simian immunodeficiency viruses (SIV), other retroviruses such as the murine leukemia virus (MLV) or the “gibbon ape leukemia virus” (GaLV) or the porcine endogenous or exogenous retrovirus (PERV), the “vesicular stomatitis virus” (VSV-G) are described. The vectors and corresponding packaging cells may be employed for packaging and transfer of genes which are not packaged by other lentiviral, retroviral and other vectors or which show an inefficient gene transfer with other vector particles. These vectors may be used for gene transfer into selected cell types, specifically into proliferatively active and resting human cells.