Abstract: Particulate fillers containing Si-OH groups are functionalized by treatment with a silica bonding agent. The treated particles are effectively polyfunctional, and may be used to prepare highly filled, cross-linked organopolysiloxane networks without the need for additional cross-linking agents. The functionalized particles are highly compatible with silicone fluids, particularly cyclosiloxane fluids. Compositions curable to such filled, cross-linked networks comprise the bonding agent-functionalized particles, a curable organopolysiloxane, and a catalyst for curing the organopolysiloxane.