The objective of this article is to evaluate quantitative implications of the hypothesis of matching, with endogenous participation, in the framework of a real cycle model. The choice of participation results from a trade off between domestic production and search for a job. Thus, fluctuations of the unemployment summarise the flows in and out of the labour force. Moreover, in this model, unemployment fluctuations are not Pareto optimal as in Andolfatto [1966] and Merz [1995]. Results of the simulations show how it is possible to explain some stylised facts of the American labour market when flows on this market are so clarified.