This article explains how an engineer might go about assessing the risk of microbiologically influenced corrosion (MIC) in an industrial situation. It describes the systems that are susceptible to the effects of MIC by sulfate-reducing bacteria (SRB). The article discusses the effects of microorganisms other than SRB on metals. SRB-related problems, which are the most common MIC issue, are also explored. The article describes the test procedures used to enumerate microbiological populations. It concludes with a discussion on risk assessment based on operating conditions.