Conventional drug delivery systems contain numerous limitations such as limited targeting, low therapeutic indices, poor water solubility, and the induction of drug resistances. In order to overcome the drawbacks of conventional pathway of drug delivery, nanoparticle delivery systems are therefore designed and used as the drug carriers. Nanoparticle based drug delivery systems have been rapidly growing and are being applied to various sections of biomedicine. Drug nanocarriers based on dendrimers, liposomes, self-assembling peptides, watersoluble polymers, and block copolymer micelles are the most extensively studied types of drug delivery systems and some of them are being used in clinical therapy. In particular for cancer therapy, antineoplastic drugs are taking advantage of nanoparticulate drug carriers to improve the cure efficacy. Nanoparticle based drug carriers are capable of improving the therapeutic effectiveness of the drugs by using active targeting for the site-specific delivery, passive targeting mechanisms such as enhanced permeability and retention (EPR), de novo synthesis and uptake of low density liposome in cancer cells or by being water-soluble to improve the suboptimal pharmacokinetics in limited water-soluble delivery methods.