This thesis discusses the utilization of natural user interfaces in the design of virtual reality mechanics. The mechanics are inspected from the perspective of interaction fidelity of virtual interactions, usability, cyber sickness, enjoyability, and feasibility. The thesis is formed out of research outlined in five scientific articles, each exploring slightly different types of natural interaction mechanics and how they could be best utilized. The mechanics include simulating real-world activities such as swimming and climbing with VR controllers, hand tracking and gesture user interfaces with one and two-handed gestures, eye tracking, and context-awareness utilizing subconscious biological reactions. The research questions outlined in this thesis attempt to find out how natural user interfaces could be constructed to be as usable as possible while simultaneously immersive, what kind of added benefits they can bring to the user experience, and what type of applications do they suit the best. The results show that a one-size-fits-all approach is not viable for natural virtual reality user interface design, highlighting how the differences in individuals affect the design requirements. The resulting conclusions are combined into an initial design framework for natural interfaces in virtual reality.