Dynamically scaled analogue models oflaccolithiç intrusions have been made. Experiments consisted of the injection of a Newtonian fluid (low-viscosity silicone putty) into a sandpack, with or without an interbedded ductile layer of silicone putty acting as a potential décollement level. Boundary conditions were chosen to analyze the influence of the thickness of the brittle cover and of the décollement layer on the pattern of intrusion. Further experiments were made to examine the effects of an extensional regime during intrusion