Participatory architecture is a form of architectural process that integrates the actual users of buildings into their concept, design, building and maintenance. Participatory approaches first began to be explored during the 1950s, perhaps as a reaction to the overly deterministic modernist architecture advocated by the Congres Internationaux d'Architecture Moderne. Various participatory practices were explored in the 1960s and early 1970s, and while they may have captured the imagination of socially-inclined architects and some clients, the result of these experiments were not widely accepted or adopted. However, experiments did have the effect of consolidating a professional and lay understanding of architecture as socially responsible.  In this thesis, I argue that architecture, as a societal tool, continues to suffer from a crisis in its inability to address the needs of the users of architecture and not merely the clients who commission the construction of buildings. Several needs of the user include adequate affordable housing, buildings properly integrated into their surroundings, ecological buildings and cities, and buildings that have the ability to disclose historical continuity and life-enhancement. In three case studies undertaken in the Plateau Mont Royal borough of Montreal, I investigate instances of user participation in formal and informal architectural projects. These case studies show how user participation can help to guide architectural projects to socially and environmentally just solutions. In an increasingly urbanized world where society is becoming progressively more polarized between the rich and the poor and where ecological devastation is becoming a reality in many cities, I argue that user participation in architectural projects is necessary if architecture is become a positive force for society.