This paper reviews the studies published worldwide on killing bacteria, fungi, prions and cancer cells using photocatalytic reaction with titanium dioxide. There are many circumstances, where removing or killing microorganisms in water, air and on surfaces is necessary or desirable. For example, water disinfection requires deactivation of pathogenic organisms. Literature on the potential use of titanium dioxide nanoparticles in daily life and in development of new self-cleaning and antimicrobial surfaces and paints along with toxicological data are also included in this review. (C) 2010 Elsevier B. V. All rights reserved.