Nanotechnology may hold the key to controlling many devastating diseases. In the fight against the pain, suffering, and death due to cancer, nanotechnology will allow earlier diagnosis and even prevention of malignancy at premalignant stages, in addition to providing multimodality treatment not possible with current conventional techniques. This review discusses nanotechnology already used in diagnostic and therapeutic applications for cancer. Also addressed are theoretic and evolving uses of nanotechnology, including multifunctional nanoparticles for imaging and therapy, nanochannel implants for controlled release of drugs, nanoscale devices for evaluation of proteomics and genomics, and diagnostic techniques that take advantage of physical changes in diseased tissue.