In this paper we present the results of MCM trials using a Biosonar system mounted on the AUV (autonomous underwater vehicle) REMUS 100. The trials were run in Lochearnhead in Scotland. Two mine-like objects were put on the seafloor. The first one was a aluminium cylinder (150 cm long and 40 cm diameter) and the second object was a truncated cone shaped aluminium shell (Manta mine like target). The REMUS 100 was equipped with a standard Marine Sonics sidescan sonar. The Biosonar payload was in a side-looking configuration. Data were gathered using both sensors simultaneously. A first set of runs covered the delimited search area using lawnmower pattern. The AUV then returned to the interesting detected objects and reacquired them following a dolphin-like spiral to obtain further data giving a range of views of the objects. The data supplied have demonstrated that the wideband sonar system is very effective at identifying seafloor objects.