During leg 3 of cruise SO81, starting in Caldera/Costa Rica at September 15th and ending in Balboa/Panama at September 28th, 1992, the first 48-channel seismic survey was carried out in the Hess Deep area as a German contribution of pre-site investigations for Leg 147 of the Ocean Drilling Programme. ODP Leg 147 is designed to drill the crust-mantle transition. During leg SO81/3 the BGR collected 662 km of seismic data and in addition gravity and hydroacoustic measurements were carried out. Profile SO81-HD001 runs W-E from and to 1 Ma old oceanic crust across the East Pacific Rise. The profiles SO81-HD002 to SO81-HD007 are located in the proper Hess Deep area passing onto the proposed drill sites. Preliminary on-board evaluation of the seismic monitor records gives a lot of interesting intracrustal reflection events which deserve more elaborate examination after proper processing of the seismic data.