Synthetic aperture sonars (SAS) and autonomous underwater vehicle (AUV) are two of the most exciting technologies under development by the underwater research and development community. Integration of these technologies promises to produce underwater acoustic imaging systems of tremendous capability and versatility. Currently, several efforts, mostly motivated by military applications, are under way to achieve the realization of these systems. This paper describes one such effort, in which the Coastal Systems Station (CSS) SAS system has been integrated with the Bluefin Reliant AUV. Included in this paper are descriptions of the CSS SAS and Bluefin AUV technology and hardware and of the data processing methods. Also presented are the preliminary results obtained during the first system tests carried out at CSS, Panama City, Florida in March 2003.