The aim of our research was to develop a quantitative assay for angiogenesis in mammals, especially the mouse. This is a convenient experimental animal because of its small size, which allows compact housing and experimentation with angiogenic factors or inhibitors in limited supply. Mouse genetics is an advanced discipline, resulting in the availability of many inbred strains and histocompatible tumors. Recombinant growth factors and other proteins are usually of human or mouse origin, and the desirability of using proteins of the experimental animal under study has been demonstrated. Mice genetically engineered to overproduce or not produce particular growth factors or receptors are valuable experimental tools.