The rapid emergence of new anticancer agents is a tremendous challenge for basic, pre-clinical and clinical research to evaluate and eventually integrate these new agents into clinical routine. Standardized, well-established in vitro and in vivo methods are available for the experimental evaluation of new anticancer agents. A step-wise procedure from in vitro to in vivo experiments using non-functional, functional non-clonogenic and, if applicable, clonogenic assays allows reduction of the number of promising agents for further clinical testing.