The condensation of alkyltrialkoxysilanes was studied using time-dependent 1H- and 29Si-NMR spectroscopy. The main goal was to correlate the results of these investigations with std. conditions in tech. applications of the most commonly used com. silane adhesion promoters. Thus, expts. with 3-aminopropyltriethoxysilane (DYNASYLAN? AMEO), 3-glycidyloxypropyltrimethoxysilane (DYNASYLAN? GLYMO) and 3-methacryloxypropyltrimethoxysilane (DYNASYLAN? MEMO) were carried out in aq. solns. at a selected range of concns. This investigation reflects a convenient way to det. the total concn. of reactive silanol groups during the course of the reaction. Moreover, the activity of the soln. in adhesion promoting processes can be monitored and measured.