Melanin biosynthesis is limited to melanocytes partly as a consequence of transcriptional regulation of the enzymes involved in this pathway. Promoter sequences of these enzyme genes may be utilised to drive expression of complementary DNA coding for therapeutic genes so as to provide transcriptional targeting. We have used the 5'-flanking sequences of the murine tyrosinase or tyrosinase-related protein 1 (TRP-1) genes to show that such transcriptional targeting can be achieved both in vitro and in vivo. Using IL-2 as an example of an immunostimulatory gene and Herpes Simplex Virus thymidine kinase (HSVtk) as an example of a prodrug-activating gene we have shown, in murine model systems, that substantial anti-tumour effects can be achieved by targeted gene therapy approaches. The stage now is set for initial clinical evaluations in human patients.