Ubiquitous computing will dramatically change our lives due to the enhancement of our real world. Augmented reality (AR) is a promising technique for realizing the enhancement by superimposing computer generated images on video images. However, it is not easy to build applications using augmented reality techniques since the developer needs to deal with issues like distribution and context-awareness. It is desirable to provide a software infrastructure to hide the complexities from programmers. In this paper, we propose a middleware called TEAR (Toolkit for Easy Augmented Reality) supporting augmented reality for ubiquitous computing environments. Our middleware provides several multimedia components that process video streams using AR techniques. New components to provide more complex functionality can be developed by composing these components.