Earthquakes for the period 1962--1973 are relocated by the method of joint hypocenter determination in order to resolve better the configuration and structure of the inclined seismic zone in the New Hebrides island arc. Twelve new focal mechanism solutions are reported and, together with previously published solutions, are integrated with the new information on the spatial distribution of hypocenters. At intermediate depths the seismic zone has a uniformly steep dip of about 70¿ and exhibits no resolvable contortions or disruptions along at least 700 km of the subduction zone. The thickness of the zone, about 20 km, may be in part due to seismically active fault zones which cut across a portion of the descending lithosphere. Features associated with the anomalous central region of the arc, where the d'Entrecasteaux fracture zone is being subducted and where the islands of Santo and Malekula appear to be in positions normally occupied by the oceanic trench, include the following: (1) an inclined zone of shallow earthquakes with very much smaller dip than is found elsewhere in the arc. (2) a pronounced gap in seismic activity at depths between about 50 and 120 km, (3) evidence for features in the upper or overthrust plate with trends transverse to the arc and parallel to the east-west trends of the topographic feature being subducted, including nodal planes of shallow focal mechanism solutions, and (4) two features which appear to coincide with the downdip projection of the northern scrap of the d'Entrecasteaux fracture zone, including a well-defined boundary between two adjacent zones of plate slippage along the main plate boundary and a faultlike feature in the intermediate depth seismic zone which also has a strike parallel to the fracture zone.