Leukaemic blast cells lack co-stimulatory molecules such as B7, necessary for T-lymphocyte activation. We have used modified CD80+ (B7-1+) tumour cells, with autologous, IL-2 producing, stromal marrow cells in a series of subcutaneous vaccinations to provide a localised environment for the enhancement of cytotoxic T-lymphocytes (CTL) in a patient with acute myeloid leukaemia (AML). Localised inflammation was evident after the fifth and sixth injections with a reduction in the number of circulating blasts in the following 2 weeks. Peripheral blood in vitro CTL activity increased 36-47% after five injections.CD4 T-lymphocytes (5.7%) expanded from post-injection skin biopsies, expressed intracellular IFNgamma and perforin when exposed to autologous B7-1+ blasts and when co-cultured with either B7-1+ or unmanipulated autologous blast cells showed proliferative responses. In this patient, co-injection of B7-1+ tumour cells, together with a local source of sustained IL-2, resulted in an autologous anti-leukaemic in vitro immune response.