The influence of cement slurry compositions with the silane coupling agents tetraethyl orthosilicate (SiL), 3-(trimethoxysilyl)-1-propanethiol (SH) and 3-(chloropropyl)-trimethoxysilane (CL) on resistance to hydrochloric acid attack has been investigated. Calorimetric results indicate the silanes enhanced the chemical resistance of the slurries. Increasing temperature decreased the time of action of the acid on the slurries. Reactivity follows the sequence: standard slurry > slurry-SiL > slurry-CL approximate to slurry-SH. (C) 2004 Elsevier B.V. All rights reserved.