All multifamily buildings must meet code requirements for fire-resistance between dwelling units, both horizontally (i.e., side by side) and vertically (i.e., above and below). They also need to meet requirements for acoustical performance such that sound transmission between dwelling units is controlled or minimized. The means for constructing these outcomes can vary depending on the types of materials and products used in floor and demising wall assemblies. One product that has been used extensively overseas is now becoming very popular in the United States as well. Boards or panels made from magnesium oxide (MgO) are showing up on projects across the country to act as a subfloor, sheathing, wall board, or underlayment material. In the process, they are bringing enhanced fire-resistance and acoustical performance to many building types, most notably multifamily projects. Based on this emerging popularity, this course looks more closely at designing and constructing with MgO panels. Beginning with a description of the material and its properties, its code compliance characteristics related to fire resistance are discussed. Recognizing the latest code requirements for acoustic control in multifamily buildings, the sound attenuation capabilities are also reviewed. Finally, a discussion of its installation, particularly compared to other alternatives such as a wet-laid gypsum underlayment, is presented. Overall, the suitability and advantages of using MgO panels is provided for consideration in the specifications and design of multifamily projects all around the country.