This article reviews the potential of polyrotaxanes in drug delivery with the historical background of polyrotaxane syntheses. Pseudopolyrotaxanes and polyrotaxanes, including classifications, synthetic methods, structures and physical properties are discussed in the first section. The second section provides our concept of drug carriers using drug-polyrotaxane conjugates in comparison with conventional drug-polymer conjugates. The third and fourth sections describe the synthetic method for biodegradable polyrotaxanes, the conjugation with drugs, and their association under physiological conditions. The fifth section discusses other possibilities for the polyrotaxanes such as drug penetration enhancers. These studies suggest the potential of polyrotaxanes in pharmaceutical applications.