Purpose - Many companies can today attest to having obtained significant progress in their performance using some improvement processes (six sigma, 5S, business process reengineering, etc.). But they can also attest to experiencing difficulties in sustaining the use of these processes over time. The aim of this paper is to describe all the specific actions which can contribute to the sustaining of these processes. Design/methodology/approach - An empirical research methodology is used by carrying out a survey of 40 Swiss and French manufacturing companies regarding their approach to the sustaining of some of their improvement processes. Findings - A model of sustainability for an improvement process is proposed. This model is founded on three axes: organic state, return on effort and facilitation. To sustain an improvement process over time consists in taking these three axes into account by managing their relative importance in space and over time. The paper details the generic actions associated with each of the three axes. These actions are then illustrated using the context of a sustained statistical process control project. Originality/value - The survey detailed in this paper confirms the difficulty of companies have in sustaining their improvement processes over time, since the average sustainability ratio for all the different processes mentioned rarely exceeds 40 per cent. The paper gives all the specific actions which can contribute to sustain these processes better.