An attempt at thermoluminescence (TL) dating of the Laschamp lava flow (Chaine des Puys, Massif Central, France) is presented. The quartz phenocrysts of a porphyric granite xenolith of the lava was used. Problems related to the distribution of radiation dose in the quartz crystal from its surroundings are discussed. Taking into account the fact that the TL growth as a function of the added dose is close to the onset of saturation, the age obtained is 34.6 x 10³ years. -- AATA