Despite recent emergence of novel therapeutic agents the major progress achieved in cancer treatments results from conventional drugs used for cytotoxic or hormone therapy. Over the past 20 years, a more rational and more pharmacological-based approach to chemotherapy has led to major successes. One of the most promising avenues of research is to improve the pharmacokinetic properties of well-known anticancer drugs (bioavailability, distribution, targeting, drug carriers) by modifications of their formulations (new drug delivery systems). As an example, new pharmaceutical forms of analogs of LH-RH, (microparticles or implants) permitting sustained release of the drug for months, are now largely used in the routine chemotherapy for prostate cancers. Improvement of the oral bioavailabilty of drugs previously administered only by the parenteral route is simplifying treatment protocols. Parenteral delivery of doxorubicine entrapped in liposomes (pegylated liposomes) decreases the cardiotoxicity and increases the half-live of this drug widely used in the treatment of breast carcinomas. Molecular targeting using immunocarriers such as immunoliposomes is also a very strong field of research.