Mesoporous silicon (PSi) is an attractive choice when considering the utilization of mesoporous materials in biomedical applications. The size of the pores, morphology and the surface chemistry of the pore walls can be easily changed and controlled making PSi a versatile material. So far, PSi has not been widely applied in commercial products, but as the knowledge of biocompatibility and toxicity is increased by further in vivo studies, the possibilities of PSi are wide in medical treatments and diagnostics. In this review, we will focus on the fabrication and chemical modifications of porous silicon for biomedical applications, but a wide variety of biomedical applications will be discussed also. (C) 2007 Elsevier B.V. All rights reserved.