The findings and recommendations of a study of potential opportunities to convert under-utilized space in multiple residential projects into play spaces for children are reported. On the basis of site visits, informal interviews and discussions with management from a selected and representative sample of 18 residential projects in the Toronto area, a typology of under-utilized spaces and the situations in which such spaces occur was developed. The opportunities available for conversion were varied, and ranged from vast underground areas, which had never been used and would require extensive refitting, to small spaces, which were no longer needed for their intended use and which could, with little effort, become useful play areas. For the most part, those spaces identified as under-utilized were indoor. Three case studies are also presented in order to provide insights into how a variety of under-utilized spaces can be redesigned to provide interesting and useful play spaces for children, and to stimulate thinking about opportunities which may exist in residential projects across the country. Case studies one through three present design exercises focused on refitting (1) a storage area, (2) a daycare facility, and (3) an underground parking garage, respectively. A checklist to help evaluate under-utilized spaces and guidelines for refitting such spaces as play spaces for children is included. Summaries of each of the 18 projects reviewed are appended. (Author/RH)