Chlorite from the Malaguide Paleozoic (Betie Cordilleras, Spain) with average composition Al_1.42Mg_1.66Fe⁺²_1.96Fe⁺³_0.64(Si_2.58Al_1.42)O₁₀(OH)₈, has been used to study the stages and mechanism of dehydroxylation. The study has been carried out by means of high-temperature X-ray diffraction, differential thermal analysis, thermogravimetry, and infrared spectroscopy. The DTA curve displays a large endothermic effect at about 600 °C, and a weak exothermic effect at 825 °C. The endothermic effect is accounted for by the loss of both the interlayer and the inner hydroxyls, which occurs through a continuous process. The loss of the interlayer hydroxyls, between 500 and 630 °C, causes the shortening of the b- and c-parameters, but the phase formed shows high crystallographic similarity with the parent structure. The formation of the 14 Å modified chlorite structure occurs after the loss of a part of the inner hydroxyls and involves, in consequence, the 2:1 octahedral layer. Differences in thermal behaviour between Malaguide chlorite and the trioctahedral chlorites of the clinochlore-chamosite series may be tentatively related to the presence of vacancies derived of the high Fe⁺³+Al content.