Stereo “3D” vision refers to the depth perception we have by virtue of viewing the world through two slightly offset eyes. This ability is receiving attention at the moment because advances in digital technology have made it much easier to display high-quality stereo media. While the basic geometry underlying stereo vision is straightforward, we are still learning how inputs from the two eyes are combined and processed within the brain to result, ultimately, in this vivid percept of depth. In this talk, I will describe current models of disparity encoding in primary visual cortex (V1), and discuss how information in V1 relates to perception.