The study of human-computer interaction within immersive virtual environments requires us to balance what we have learned from the design and use of desktop interfaces with novel approaches that allow us to work effectively in three dimensions. This dissertation presents empirical results from four studies into different techniques for indirect manipulation in immersive virtual environments. These studies use a testbed called the Haptic Augmented Reality Paddle (or HARP) system to compare different immersive interaction techniques. The results show that the use of hand-held windows as an interaction technique can improve performance and preference on tasks requiring head movement. Also, the use of a physical prop registered with the visual representation of an interaction surface can significantly improve user performance and preference compared to having no physical surface. Furthermore, even if a physical surface is not present, constraining user movement for manipulating interface widgets can also improve performance. Research into defining and classifying interaction techniques in the form of a taxonomy for interaction in immersive virtual environments is also presented. The taxonomy classifies interaction techniques based on three primary axes: direct versus indirect manipulation; discrete versus continuous action types; and the dimensionality of the interaction. The results of the empirical studies support the classification taxonomy, and help map out the possible techniques that support accomplishing real work within immersive virtual environments.