This paper provides a structural estimation of an equilibrium search model with on-the-job search and heterogeneity in firms’ productivities using a sample of Italian male workers. Results indicate that arrival rates of offers for workers are higher when unemployed than when employed and firms exploit their monopsony power when setting wages. As a result, workers earn far less than their marginal product. The model is then used to study regional labour market differentials in Italy. Wide variation in frictional transition parameters across areas helps to explain persistent unemployment and wage differentials.