Bluetooth (BT) is presently the primary wireless technology for short range Personal Area Networks (PAN). Piconet is the basic unit of networking in BT that contains one master and from one to seven active salve devices. Piconets can be interconnected to form a Scatternet. Scatternet formation and routing are the important areas on which considerable research has been done so far. Security is another important issue for BT scatternets. BT specification provides security measures for Piconets but secure communication in a scatternet is an open problem. In our research we specifically consider routing security in BT scatternets. We describe a number of routing threats and then present an authenticated routing scheme which is based on Zone Routing Protocol. We evaluate the scheme through simulation and show that it effectively secures the route discovery process in BT scatternets.