For computer assisted surgical simulation to be effective, objects in the simulated environment should respond to the user's actions dynamically with correct visual information. This includes dragging and cutting that cause changes in geometry, topology and appearance. Geometric object representation can be manipulated intuitively in real-time but does not preserve interior information. Volumetric data representation, on the other hand, preserves volume content but direct manipulation is compute-intensive. 3-D texture mapping provides an alternative in representing volumetric information. We present a surgical simulation system based on geometric models that allows interactive deformation and incision of objects while displaying correct volumetric information corresponding to these changes. This is accomplished by dynamic 3-D texture mapping. This method can be applied to anatomical data and patient CT and MR images to facilitate data/patient specific surgical simulations.