Thirty potsherds ranging from Tzec (Mamon) to Caban (EarlyPost-Classic) Maya were examd. for concns. of 21 chem. elements and cryst. content. Quartz was less abundant in later sherds but the silica:alumina ratio tended to be high, 4:1, implying considerable addn. of siliceous material. Calcite was less abundant in later sherds; the earlier practice of adding low-Sr limestone as temper seems to have been abandoned. Potash concn. decreased with time while the Rb:K ratio declined; potash may tlius have come from a biol. source, e.g., wood ash. Though El Bajo de Santa Fe clay, the nearest source to Tikal, was not used, a like montmorillonite was employed by the Tikal potters. Chem. anal. of trade sherds, 1 from Tzec, another from the Eznab, and 2 from the Caban Complex type differ from the local ones; 3 of the locals are alike in high Fe, Ti, Mg, Co, Ni, and Cr contents, and the materials in these pots may have come from highlands south of Tikal. From Ik to Caban firing temp. seems to have dropped as the culture waned; all trade sherds were fired at the lower temp. range. Feldspar present in early and late periods was absent in the interim periods, and it is not to be found in locally obtainable material. A pot from the modern pottery center at Ticul showed feldspar as its only cryst. component. -- AATA