This paper presents the results of the investigation of the hydration of alkali-activated slag (AAS) by nuclear magnetic resonance spectroscopy (NMR). The cross-polarization (CP) technique was used in combination with magic-angle spinning (MAS). This research was part of a systematic study of alkaline activation of slag by several different techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with X-ray microanalysis of energy dispersive spectra (EDS), differential thermal analysis (DTA) and calorimetry. This NMR study provides information on the polymerization of silicates, the role of aluminates in cement hydration and the nanostructure of C-S-H gel. © 2002 Published by Elsevier Science Ltd.