In accordance with the present invention, disclosed is a method of conferring, upon a host cell, resistance to retroviral infection by interfering with one or more of the infection processes including retroviral replication and assembly into infective viral particles. The method involves introducing a vector into a host cell, wherein the vector comprises a polynucleotide which directs transcription, within the host cell, of RNA which is a) complementary or homologous, depending on the target region, to a nucleic acid sequence within one or more regions of the genome of the retrovirus; and b) is effective in inhibiting retroviral replication and/or interfering with assembly into viral particles when the host cell is infected. Also disclosed is a method of treatment using cells upon which resistance to infection has been conferred.