Abstract: A pregrouted base plate and the method of its use and construction with rotating machinery such as pump and electric motor assemblies that are coupled together by a pair of shafts and require precise alignment of those shafts for a long and dependable service life is disclosed. The pregrouted base plate is formed as a generally rectangular parallelepiped structure with one side open. The novel method of its use includes pregrouting the baseplate before installation, curing the grout and machining the mounting surfaces for the rotating machinery before field installation to ensure precise alignment of the pump and motor shafts. A second embodiment is shown with an open frame having two sides open.