Augmented Reality (AR) is an active and exciting topic aiming to create intuitive computer interface by blending reality and virtual reality. One challenge of AR is to align virtual data with the environment. Typically, one uses a marker-based approach such as a thick-bordered black and white 2D marker which allows one to recover the relative pose (location and orientation) of a camera in real time. However, bar-code markers do not contain any intuitive visual meaning, and they thus look uninteresting and uninformative. We propose a new type of marker, referred to as a StereoTag, which embeds a meaningful stereogram image hiding 3D coded/decoded information. From experiments conducted, our StereoTag is found to be relatively robust under various conditions and thus could be widely used in future AR applications.