Fluctuations, drifts or performance abnormalities in the scintilation gamma-ray spectrometer may completely invalidate its calibration and, under any circumstance, will lessen its precision of measurement. In this report, a technique patterned after well-established methods of quality control is described for both establishing and maintaining instrument stability. In the past, methods for spectrometer stabilization or for compensation of instability effects have made no provision for evaluating instrument performance. In the present method, corrections for instrumental drift are determined by a process of periodic sampling. In addition, from the sampling data, evaluations of important performance qualities are made and the results are logged. Using the log as a guide, factors affecting instrument stability have been brought under control and instrument reliability has gradually improved with a resultant reduction in the requirement for special maintenance.