The infrared spectrum of water adsorbed on K-hectorite has been studied in the frequency range 2600–4000 cm−1 on samples equilibrated with relative humidities of 0% to 100%. The model proposed by J. Mamy for the molecular array of water upon the mineral surface has been used as a starting assumption. A ‘unit cell’ made of two H2O molecules is then considered as a possible theoretical basis for the interpretation of the infrared spectrum. When taking into account this unit cell six stretching frequencies may be anticipated. The six components of the OH stretching band are clearly resolved at −95°C at room temperature a Curve Resolver was used to analyse the composite band, which was recorded at various incident angles (0–45°). From the variation of the integrated absorption of each component band given by the curve resolver, the orientation of the dipolar moment is calculated, and compared with the theoretical one deduced from the model.