Bulky head-mounted displays, data gloves, and severely limited movement have become synonymous with virtual environments. This is unfortunate, since virtual environments have such great potential in applications such as entertainment, animation by example, design interface, information browsing, and even expressive performance. In this article, we describe an approach to unencumbered natural interfaces called Perceptive Spaces. The spaces are unencumbered because they utilize passive sensors that do not require special clothing and large format displays that do not isolate the users from their environment. The spaces are natural because the open environment facilitates active participation. Several applications illustrate the expressive power of this approach, as well as the challenges associated with designing these interfaces.