During the Polish Antarctic Geodynamical Expeditions in 1979-91, deep seismic sounding measurements were performed in the transition zone between the Drake and South Shetland Microplates and the Antarctic Plate in West Antarctica. For the Bransfield Strait area, the seismic records of five land stations in South Shetland Islands and two stations at the Antarctic Peninsula were used. The interpretation yielded two—dimensional models of the crust and lithosphere down to 80 km depth. In the uppermost crust, the unconsolidated and poorly consolidated young sediments with velocities of 1.9 — 2.9 km/s cover the layers 4.0—4.2 and 5.6—5.9 km/s. The crustal structure beneath the trough of Bransfield Strait is highly anomalous. The presence of a high velocity body, with longitudinal seismic wave velocities vp > 7.0 km/s, was detected in the 6 — 30 km depth range. This inhomogeneity was interpreted as an intrusion, coinciding with the Deception—Bridgeman volcanic line. For the uppermost crust, a qualitative comparison was made between the results from the reflection profiles (GUN) and deep seismic sounding profiles (DSS). In the study area, the Moho boundary depth ranges from 10 km beneath the South Shetland Trench to 40 km under the Antarctic Peninsula. In the transition zone from the Drake Passage to the South Shetland Islands, a seismic boundary in the lower lithosphere occurs at a depth ranging from 35 to 80 km. The dip of both the Moho and this boundary is approximately 25°, and indicates the direction of subduction of the Drake Plate lithosphere under the Antarctic Plate. The results obtained were compared with earlier results of seismic, gravity and magnetic surveys in West Antarctica. A scheme of geotectonic division and a geodynamical model of the zone of subduction of the Drake Plate under the Antarctic Plate is compared with subduction zones in other areas of the circum-Pacific belt.