The structural changes of three hectorites during dehydroxylation have been studied using Infrared emission spectroscopy of the hydroxyl stretching and bending regions. The hydroxyl stretching region is characterised by two hydroxyl stretching modes around 3647 and 3672 cm(-1). These bands decrease in intensity upon dehydroxylation up to 750 degrees C but do not completely disappear. Above 250 degrees C a new band attributed to silanol groups becomes visible around 3741 cm(-1) in all samples due to transfer of the hydroxyls from the octahedral layer to the siloxane layer before they are lost. The presence of two different hydroxyl groups is also reflected in the hydroxyl deformation modes around 657 and 695 cm(-1). These bands show a decrease in intensity upon heating and dehydroxylation of the day structure. A new broad band becomes visible at high temperature, which is ascribed to the formation of pyroxene-like (MgSiO3) units. The infrared emission spectra do not give any evidence of what happens to the lithium and other interlayer alkalies during the dehydroxylation but it is inferred that the lithium is incorporated in an amorphous silica phase.