Data acquired by ocean bottom seismometers (OBS) can give better constraints on the velocity structure of deep basins, allowing estimates to be made of pore pressure in deep sediments. The Black Sea is a deep sedimentary basin with a thick infill of ∼9 km, and is a frontier basin for hydrocarbon exploration. Mud volcanism, associated with overpressured sediments is observed in the basin. To our knowledge, the magnitude of excess: pore pressure has not been quantified, in part because conventional reflection data cannot resolve the velocity structure in the deepest part of the basin. In spring 2005, four wide-angle seismic profiles were collected across the basin. Tomography modelling of the data has allowed us to construct a relatively detailed sediment velocity model, including the presence of a low velocity zone. The anomalous velocities within this zone are too low to be associated with lithology changes and are assumed to be overpressured sediments. The excess pore pressure can be estimated by relating effective stress to seismic velocity. We have used two different methods to place conservative estimates on pore pressure. Both methods predict pressures of ∼150 MPa at the base of the overpressured zone, which represents ∼80% of lithostatic pressure.