Since the first human gene therapy clinical trials were proven successful in 2000, human gene therapy has witnessed setbacks as well as encouraging progress. While these first clinical trials were performed with a γ-retrovirus vector to correct X-linked severe combined immunodeficiency (SCID-X1) in children, others since then have applied similar or alternative viral vector strategies. More recently, lentiviral vectors have been used for the correction of human β- thalassaemia and adrenoleukodystrophy. They have also been successfully used in the treatment of leukaemia by modifying cytotoxic T cells directed to cancer cells. Here we describe the production of clinical grade retro- and lentiviral vectors for application in human therapy.