This paper examines the importance of credit demand and credit supply-related factors in explaining the evolution of credit granted to Portuguese small and medium-sized enterprises (SMEs). The results suggest that the interest rate is a strong driver of SMEs' demand for bank loans, as well as their internal financing capacity. On the other hand, credit supply mostly depends on the firms' ability to generate cash-flows and  reimburse their debt, and on the amount of assets available to be used as collateral. The model was estimated for the period between 2010 and 2012, and the estimated coefficients were used to compute the probability of credit rationing. The results suggest that a considerable fraction of Portuguese SMEs were affected by credit rationing in this period.