Three-dimensional capabilities on mobile devices are increasing, and interactivity is becoming a key feature of these tools. It is expected that users will actively engage with the 3D content, instead of being passive consumers. Because touchscreens provide a direct means of interaction with 3D content by directly touching and manipulating 3D graphical elements, touch-based interaction is a natural and appealing style of input for 3D applications. However, developing 3D interaction techniques for handheld devices using touch-screens is not a straightforward task. One issue is that when interacting with 3D objects, users occlude the object with their fingers. Furthermore, because the user's finger covers a large area of the screen, the smallest size of the object users can touch is limited. In this thesis, we first inspect existing 3D interaction techniques based on their performance with handheld devices. Then, we present a set of precise Dual-Finger 3D Interaction Techniques for a small display. Then, we present the results of an experimental study, where we evaluate the usability, performance, and error rate of the proposed and existing 3D interaction techniques. Finally, we integrate the proposed methods of different user modes.Keywords: mobile 3D environments, touch-screens, multi-touch input, dual-finger techniques, modular interaction.