Abstract: Recent research on high-performance ray tracing has achieved real-time performance even for highly complex surface models already on a single PC. In this report, we provide an overview of techniques for extending real-time ray tracing also to interactive volume rendering. We review fast rendering techniques for different volume representations and rendering modes in a variety of computing environments. The physically-based rendering approach of ray tracing enables high image quality and allows for easily mixing surface, volume and other primitives in a scene, while fully accounting for all of their optical interactions. We present optimized implementations and discuss the use of upcoming high-performance processors for volume ray tracing.