Abstract : We use a disequilibrium model to estimate credit rationing to Small and Medium-sized Enterprises (SMEs) on the Tunisian bank credit market. Based on a panel dataset of 1,275 SMEs over the period 2001-2006, results show that the demand for bank credit is not determined by " endogenous " factors, i.e. the activity level and internal available resources of SMEs, but rather by " exogenous " factors, i.e. the cost of financing and guarantees required by banks. The latter, especially real guarantees, explain to a large extent the lack of bank lending and results in an average share of 80% — partially or totally — credit rationed SMEs.