The Rosse-Panzar statistic is used to test for market conduct and contestability within the UK building society mortgage market between 1990 and 1996. Tlie statistic considers the distinction between monopolistic competition and profit maximising monopoly. Following Panzar and Rosse , analysis of monopolistic competition can be seen to be concerted with both an individual and a group equilibrium. The comparative static approach of the Rosse-Panzer statistic is employed to test for this situation. Evidence of long-run competitive equilibrium is rejected. Presence of a contestable market with monpolistic competition is not rejected.