This paper describes the state of the art Mass Properties Laboratory at the McDonnell Douglas Helicopter Company in Mesa, Arizona. The lab's prime capabilities include: weight and center of gravity measurement; static balancing of helicopter main rotor blades; inertia measurement; and dynamic balancing of helicopter rotor hubs, complete tail rotor assemblies, and NOTAR (No Tail Rotor) fans. The theory behind the operation of each system as well as its basic requirements is described in detail. These requirements involve accuracy, repeatability, linearity, simplicity, maintainability, calibration and temperature correction, and size and weight limits. The mass properties lab and its features are the result of management foresight and cumulative years of experience in mass properties engineering. This lab, along with the entire Advanced Development Center in which it is housed, demonstrates the commitment of McDonnell Douglas Helicopter Company to be on the leading edge of technology.