This article presents a comprehensive and critical discussion of available literature on conductivity wire mesh tomography as well as some complementary original analysis. Wire-mesh tomographs were first classified into different categories, depending on their principles of operation, and then the discussion was focused on the most commonly used type, namely, the wire mesh sensor (WMS) in vertical channel flows. The main applications of WMS were outlined and the properties that can be determined from WMS signals were identified, together with the corresponding procedures. WMS performance and the factors that affect this performance were evaluated in detail using results of previous investigations as well as new analysis and data. The principles of operation and main applications of global wire mesh tomographs were then described. This article finally presents several examples of wire mesh tomography applications in multicomponent flows.