This paper describes typical anti-microorganism chemicals used in hospitals, and touches on measures against intra-hospital infection. Killing microorganisms reliably by using a high-pressure steam sterilization method is the best means for medical devices and apparatuses. However, there are high-priced medical devices that cannot withstand such a method and require other processes according to the situations, such as gas sterilization and alcohol disinfection. In addition to such sterilization methods as using heat, alcohols, and gases, methods that have been developed recently may include the following: use of Bronopol (an antiseptic) and anti-mold agents that have electronphilic functional groups, disinfectants using metal ions from silver, zinc and copper, and other materials. The problem of intra-hospital infection is caused typically by MRSA, hepatitis virus and Pseudomonas aeruginosa. Preventive measures require good knowledge about their infection courses and disinfecting technologies, as well as an attention not to cause change in the ecology as a result of using excessively strong chemicals. 18 refs., 1 fig., 1 tab.