In this paper we review empirical studies concerning the effectiveness of stereoscopic displays in medicine. The domains covered in this review are: diagnosis, pre-operative planning, minimally invasive surgery (MIS) and training/teaching. For diagnosis, stereoscopic viewing of medical data has been shown to improve the sensitivity of tumor detection in breast imaging, and to improve the visualization of internal structures in 3D ultrasound. For MRI and CT data, where images are frequently rendered in 3D perspective, the added value of binocular depth has not yet been convincingly demonstrated. For MIS, stereoscopic displays decrease surgery time and increase accuracy of surgical procedures when the resolution of the stereoscopic displays is comparable to that of 2D displays. Training and surgical planning already use computer simulations; more research however is needed to assess the potential benefits of stereoscopic displays in those applications. Overall, there is a clear need for more empirical evidence that quantifies the added value of stereoscopic displays in medical domains.