Loop-mediated isothermal amplification, LAMP, has attracted the interest of the scientific community due to several of its advantages over classical nucleic acid amplification (NAA) techniques, namely, PCR and qPCR, as well as over other isothermal techniques such as NASBA, HDA, and/or RPA. However, the design of multiplex assays remains challenging. This issue is critical if considered that for specific applications, an amplification control, which ideally would be internal (IAC), is already mandatory for methods based on the application of PCR/qPCR. In the current chapter, we will guide the reader on how to design a competitive IAC for its successful implementation in a multiplex assay.