Previous studies have documented the tendency for the commercial banking sector of many developing economies to be highly liquid and be characterised by a persistently high interest rate spread. This paper embeds these stylised facts in an oligopoly model of the banking firm. The paper derives both the loan and deposit rates as a mark up rate over a relatively safe foreign interest rate. Then, using a diagrammatic framework, the paper provides an analysis of: (i) the distribution of financial surplus among savers, business borrowers and banks; (ii) exogenous deposit shocks; (iii) exogenous loan demand shocks; and (iv) the impact of interest rate control on financial intermediation