Definitive observation of interplanetary magnetic fields depends not only upon the development of high sensitivity spaceflight magnetometers but also on the availability of spacecraft having negligible disturbance fields. Test results obtained in the Pioneer VI-IX program have demonstrated that through careful design, spacecraft magnetic fields can be reduced by a factor of 25 so that spacecraft field levels of 10-6 gauss or less can be realized. Since the literature contains little information on the magnetic properties of spacecraft parts and materials, low-magnetism design principles and low-field magnetic testing techniques, those recently concerned with low-magnetism design may be working with only a small fraction of the information currently known. A critical review of the current state-of-the-art for low-magnetism spacecraft design and test is presented