Approximately 325 quartz resonators have been fabricated or purchased and measured for aging and reliability at 85 C over periods up to 14 months. These have been divided among low frequency (100 to 500 kc), 3 Mc, 10 Mc and 16 Mc resonators and among natural, cultured, and electrolytically swept natural and cultured quartz. Data accumulated by electrical measurements and by visual and x-ray diffraction methods have been analyzed in order to determine mechanisms responsible for the principal aging vectors observed. Measured reliabilities are reported. Of 96 low frequency resonators only 46% passed the initial aging requirements of 5 ppm during the first 30 days. Three of these failed to subsequent requirement of 2 ppm each 30 days thereafter giving a reliability of 94% for a 6 month period. Analyses by x-ray diffraction methods revealed strains associated with the quartz blank fabrication and mounting methods. Edge grinding, silver spotting, plating separation by airbrasive, quartz defects, and strained mounts, all appeared as possible contributors to high positive aging rates.