We report four studies in which we investigated the production of spatial discourse designed to help people move around in unfamiliar environments. In Study 1, descriptions of three routes were collected from residents of the city of Venice. Analysis of the descriptions revealed the variety of ways used to describe each route. Typical features of route directions were found, in particular the uneven distribution of the landmarks mentioned, which tended to concentrate at critical points where an orientation problem had to be solved. Study 2 used individual protocols to construct more abstract (skeletal') descriptions, reยฏecting the essentials needed for navigation. New subjects selected those units of information they judged necessary and sucient to guide a person travelling along the routes. The contents of the skeletal descriptions were very similar, whether they were established by people familiar with Venice or complete strangers, suggesting that people can judge the relevance of information in route directions, regardless of their knowledge of the environment described. Study 3 showed that the ratings of the communicative value of the original individual protocols also resulted in very similar responses from familiar and unfamiliar judges. Finally, Study 4 assessed the value of individual descriptions for assisting navigation by testing the navigational performance elicited by these descriptions. Subjects unfamiliar with the city of Venice were given skeletal descriptions or descriptions which had been rated good' or `poor' in the previous study. Navigation with good descriptions gave signiยฎcantly lower error scores than navigation with poor descriptions, and skeletal descriptions gave scores similar to those of good descriptions. Poor descriptions also resulted in more errors from subjects who tended to use a survey perspective than from subjects expressing a preference for visual memories of landmarks. We suggest that the eciency of route directions as navigational aids depends not only on their intrinsic characteristics but also on the mode of processing adopted by the users.