Human gene therapy in 1996 is a reality with almost 100 trials world-wide involving nearly 450 patients. The stakes are enormous. To assure the efficacy and safety of such a regime is mainly a problem of vector to carry the chosen nucleotide sequences. The ideal vector should have as a unique function that of the transport of the gene of therapeutic interest to the desired area at the proper quantity. The ideal vector does not currently exist and each system, viral or non-viral has both advantages and inconveniences.