An accurate perception of the distance between an object and a nearby surface can increase a viewer's sense of presence in an immersive environment, particularly when a user is performing actions that affect or are affected by this distance. Two experiments were conducted examining the effectiveness of stereoscopic viewing, shadows, and interreflections at conveying this distance information. Subjects performed simple tasks based on the perception of the distance between a fixed virtual table and an approaching block in a virtual environment. In the first experiment, subjects lowered a virtual block to a virtual table. For this task, both stereoscopic viewing and shadows had statistically significant effects on subject performance. In the second experiment, subjects mechanically reported the perceived distance between a virtual block and virtual table. For this task, viewing condition, shadows, and interreflections were shown to be statistically significant distance cues.