There are many ways of employing such light enhanced targeting in very many locations within the body. When it is applied to direct killer T-cells to ovarian primary tumours, not only is primary tumour growth markedly reduced but also a dramatic reduction of metastatic growth is observed in the liver. In this article Stephen Thompson, Alexander C. Selfand Colin H. Self describe how photo-activation technology will improve the targeting of therapeutic conjugates to tumours by increasing their effective specificity. When used in conjunction with improvements in recombinant antibody production techniques and rapidly evolving light-delivery systems, it should be possible to build a wealth of extremely effective, highly tumour-specific therapies in the near future.