This thesis presents the results of a number of phase I studies with new target specific growth inhibitory or cytostatic anticancer agents, administered as single agent or in combination with cytotoxic chemotherapy. The new target specific agents studied are an epidermal growth factor receptor tyrosine kinase inhibitor, a farnesyltransferase inhibitor and an angiogenesis inhibitor, respectively. Whereas the first two agents act on targets that are located in the cancer cell wall and within the cytoplasm, respectively the third agent is specifically developed to inhibit the formation of new blood vessels in the peritumoral stroma.