New light is shed on the enigmatic Rhodes deep marine basin by a set of underway geophysical data across it, including swath bathymetry, seismic reflection profiles, gravity and magnetic data. This deep trough (as much as 4485 m) to the east of the Island of Rhodes and close to southwestern Turkey, contains no Messinian evaporites and only a thin Pliocene-Quaternary sedimentary section (< 1000 m) overlying an acoustic basement. This basement is likely composed of pre-Miocene tectonized rocks tentatively related to neighbouring Hellenide-Tauride alpine orogens. Reverse faulting, strike-slip faults, sedimentary nappes and mass sliding are presently occurring in the Rhodes Basin mainly around its edges. This tectonic activity, together with a relatively important seismicity (particularly along its northwestern margin), indicates that the basin is still evolving. We suggest that the Rhodes Basin results from a general collapse of what is now its brittle basement, in connection with the progressive development of transform motion along the eastern branch of the Hellenic Arc. If our hypotheses are correct, the Rhodes Basin is a relatively recent (post-Miocene) foundered trough, somewhat similar to pull-apart basins which have also developed along the transpressive branch of the Hellenic subduction zone, particularly along the Pliny Trench. (C) 2000 Elsevier Science B.V.