To test whether the weakening effect of added water in ductile deformation experiments on quartzite at high P-T conditions is associated with measurable changes in intragranular water content (c_w ) we determined Fourier transform infrared (FTIR) spectra of single grains (grain size 150–250 μm IR spot size ∼70 μm) in samples of Dongelberg quartzite experimentally deformed in a Griggs solid-medium deformation apparatus at a temperature of 800°C, a confining pressure of ∼1200 MPa, and a strain rate of ∼10⁻⁷ s⁻¹, both with and without ∼0.4 wt % added water. The added water caused a weakening effect of a factor ≥9. Microstructural observations indicate that the dominant deformation mechanism in the weakened samples was solution-precipitation creep. The FTIR measurements showed that the starting material has a broad variation in c_w as well as in the type of OH absorption. The c_w of individual grains range from <200–2900 molar ppm H/Si (measurement resolution: 100–1000 molar ppm H/Si; standard error of average c_w values 300–900 molar ppm H/Si). The experimentally deformed samples, whether deformed with or without added water, showed a broadly similar variation in c_w with similar types of OH absorption. Relatively “dry” grains (<100–500 molar ppm H/Si) were still present in the samples deformed with added water, as well as relatively “wet” grains (>3000 molar ppm H/Si) in samples deformed without added water. We were unable to demonstrate any significant changes in average c_w after either of the treatments. Apparently, the water weakening effects seen in our experiments occurred without measurable changes in c_w .