As scientific laboratories are an important domain of application of VR technology, ethical issues of VR have to be discussed with respect to research and the treatment of research subjects. Exposing participants to VR systems may raise ethical problems due to motion sickness, information overload, intensification of experience, and difficulties with reentry into the real world. The ethical guidelines which are typically applied to psychological research do not cover all of these problems in detail and have to be reconsidered, since they have not been developed with regard to the use of VR systems. Therefore, practical strategies to cope with the addressed ethical problems in VR research are recommended.