Proton-exchanged montmorillonite (H+-montmorillonite) was found to be a heterogeneous catalyst for allylsilylation of alkenes with allylsilanes. A wide variety of aromatic and aliphatic alkenes were effectively converted to the corresponding allylsilylated products in 15-120 min at 60-100 degrees C using H+-montmorillonite with ca. 1-2 wt% of water. The increasing of the amount of water drastically accelerated the allylsilylation of alkenes. For example, the reaction of p-chlorostyrene with allyltrimethysilane afforded 90% yield of the product for 15 min at 40 degrees C using H+-montmorillonite with 8.8 wt% of water, whereas only 2% yield of the product was obtained with 1.3 wt% of water. However, the final product yields with H+-montmorillonite with 1-2 wt% of water were higher than that with the 8.8 wt% of water. A reaction mechanism including the formation of a disilylpropyl cation was proposed. One possible explanation for the role of water is stabilization of the active disilylcation on the montmorillonite surface and/or edges via electron donation from water molecules. (C) 2013 Elsevier B.V. All rights reserved.