Certain adults, migrants or native French speakers, suffer from language insecurity, i.e. they have repertoires that are incomplete or are too unvaried to deal efficiently with the different communications situations they participate in, in particular those that fall outside the usual limits of their interactions. The duration and the scale of recent economic and social changes mean that there is little scope for these people in the labour market, and they are socially marginalized. Some of these people participate in integration or insertion initiatives that sometimes include language training. The authors define language insecurity according to this situation and they show how it can be useful for analysing the reality it describes and for suggesting solutions in adulte ducation.