The present article evaluates the knowledge that can be attributed to the application of « Best Practices » in the field of urban habitat. It especially aims at identifying the conditions of innovation in such a setting, as well as defining the necessary circumstances for an enlargement – or even the replication - of « Best Practices ». The analysis is based on the study of programs and projects carried out by the NGO “Habitat-Cuba” between 1994 and 2001. Two key aspects of the question will be highlighted: the “powers’ peripheral character of this type of programs and the “suspension” of a certain number of standards as a condition for success. The article thus underlines the fragility of these experiences in the longer term.