Abstract: A method of increasing the bioavailability upon oral administration of a pharmacologically active target agent, particularly an antitumor or antineoplastic agent which exhibits poor or inconsistent oral bioavailability (e.g., paclitaxel, docetaxel or etoposide), comprises the oral co-administration to a mammalian patient of the target agent and an oral bioavailability-enhancing agent (e.g., cyclosporin A, cyclosporin D, cyclosporin F or ketoconazole). The enhancing agent may be administered orally from 0.5-24 hrs. prior to the oral administration of one or more doses of the target agent, substantially simultaneously with the target agent or both prior to and substantially simultaneously with the target agent.