The present invention relates to the use of thermosetting polyurethane urea reactive adhesive compositions which are stable at ambient temperature but rapidly set at higher temperatures, wherein the adhesive comprises stabilized finely-divided polyisocyanates of retarded reactivity of which 0.1 to 25% of the NCO-groups are surface-modified and higher and/or lower molecular polyamines (optionally with polyols as additional reactive components). An important feature of these thermosetting reactive adhesive compositions is their capacity for storage at ambient temperature and their spontaneous increase in viscosity at relatively low heating temperatures which prevents the adhesive from running off during the heating period when applied to vertical surfaces.