A recent report by Weymouth <i>American Antiquity, 38, 339-344, 1973) on the use of x-ray diffraction techniques in the analysis of prehistoric pottery is discussed. Weymouth's pottery necessitates a reevaluation of what x-ray diffraction studies mean behaviorally. X-ray diffraction will not screen out naturally occurring inclusions in the clay from those added by potters; consequently, x-ray data based on mineral ratios cannot necessarily be interpreted culturally as temper added by potters. -- AATA