Abstract: Architects widely resort to sketch during their early phase of design, because sketching appears to be the most adapted mean to express and to manipulate creative ideas. In order to assist the designers during this inventive phase of work we have developed EsQUIsE-SMA, an on-line system for capturing and interpreting architectural sketches. This prototype is based on a MAS, MultiAgent System, which enables real time management of recognition scenarios. This paper describes the basic mechanisms involved by EsQUIsE-SMA to interpret free hand architectural drawings : the sketch as an evolutive environment, the agent types for stroke analysis and the collaboration modes between agents. The conclusions deduce the salient characteristics for a MAS dedicated to sketch analysis.