The environment is defined as a collection of visible real surfaces in space. An isovist is the set of all points visible from a given vantage point in space and with respect to an environment. The shape and size of an isovist is liable to change with position. Numerical measures are proposed that quantify some salient size and shape features. These measures in turn create a set of scalar isovist fields. Sets of isovists and isovist fields form an alternative description of environments. The method seems relevant to behavioral and perceptual studies in architecture, especially in the areas of view control, privacy, ‘defensibility’, and in dynamic complexity and spaciousness judgements. Isovists and isovist fields also shed light on the meaning of prevalent architectural notions about space. In the latter role it is hoped that an information-field theory such as the one presented can help provide fruitful common ground for designers and researchers.