We present a two-stage concept for risk reduction in craniofacial surgery, consisting of preoperative risk modeling and intraoperative risk reduction. Preoperatively it is important to find and to visualize risk sources in order to minimize them. Our risk model is composed by superimposition of an isotropic risk potential and an anisotropic tissue field constituent. It is being applied to preoperative planning and simulation of craniofacial surgeries, for example to determine an access path with least overall risk value. In the operation room risks arise mainly from the absence of preoperative planning and simulation data in the operation field. We use a see-through head-mounted display to optimize this situation in order to allow the surgeon to maintain accuracy in the whole process of computer aided surgery. Main steps of the intraoperative immersion are optical tracking of the surgeon wearing the head-mounted display and of the patient, registration of preoperatively calculated planning data with the patient and visualization of the data within the glasses.