The conditions are considered under which thermoluminescence (TL) dating can be applied to minerals subjected to ancient baking. Various specimens, listed in increasing age (in years before 1950 B. P. where specified), were dated by the method: (1) quartzite from the preceramic level of Peru (4790 B. P. ), Magdalenian sandstone (11,300 and 14, 500 B. P.), Mid-atlantic rift basalt (103,000), microgranite and biotite associated with pre-Neanderthal human remains (126,000), and obsidian from Afarr (470,000 and 59,000 years). The uncertainty of the TL dates increases with the age of the specimen and is plus or minus 8.6% for the quartzite and sandstone but reaches plus or minus 14% for the obsidian because of unevenly distributed U and Th in the samples. The TL dates of the quartzite and sandstone are reasonable based on comparison with ¹⁴C dates. -- AATA