Recent developments in the design and application of SQUID magnetometers to biomagnetic measurement is reported. It has become well established that magnetic fields are produced by electrical currents associated with muscle and nerve polarization and depolarization. Since magnetic measurements are noninvasive and body tissues are magnetically transparent, biomagnetic techniques are being explored as a promising new observational method. Magnetic fields produced by the human body have very low strength; by compari-son, Earth's ambient field is 106 larger. Definitive measurement of such weak signals in the presence of large, and in most cases unavoidable, ambient noise levels has placed difficult but not insurmountable requirements on the design and use of magnetic instrumentation. Recent developments in SQUID sensor technology have resulted in significantly reduced susceptibility to noise and increased sensitivity. SQUID sensors are currently available that achieve a high level of common-mode noise cancellation. An overview of the basic principles used to achieve this noise reduction, the types of sensors available, and the laboratory techniques for human biomagnetic measurement is presented.