Recent data from the New Hebrides (Vanuatu) subduction zone have enabled a morphological description and tectonic interpretation to be made of the complex plate contact between the d'Entrecasteaux Zone and the West Torres Massif on the one hand, and the old Santo-Malekula block on the other. Between latitudes 14'30' and 17"s no trench occurs owing to the presence of the old rigid Santo-Malekula block at the edge of the overriding plate. The outer limit of plate contact describes a tortuous line westward of the projected line of the adjacent trenches. This may be explained by local collision of the North d'Entrecasteaux Ridge, and the South d'Entrecasteaux Chain with the west flank of Santo. This collision is compensated for by lateral plastic flow of the inner wall downward into the small basins which separate the d'Entrecasteaux Zone ridges, a process which may be explained by plastic plane strain theory. The westward Jump of the plate contact zone here may result from pieces of the North d'Entrecasteaux Ridge being cut off and incorporated in the frontal arc. A review of the geological evidence and the shallow seismicity of the central New Hebrides shows that radiant horizontal stresses resulting from this collision have generated a specific compressive stress regime which influences the whole width of the arc. The resultant deformation shows a close resemblance to a theoretical strain field produced by the indentation of a long, narrow, plastic body (cf. the arc) by a rigid, flat die (cf. the d'Entrecasteaux Zone). Thus the central New Hebrides block is both elastically bent under vertical stresses and plastically deformed and pushed eastwards by horizontal stresses. Recent uplift of the eastern chain can be explained by this model. In contrast, at the rear of both the northern and southern sections of the arc the tectonics are mainly controlled by a tensional stress regime. The strong plate interaction due to the subduction of the d'Entrecasteaux Zone is thought to be responsible for the compressive stress regime across the central New Hebrides. The same cause can be invoked to account for the tensional stress regime observed in north and south New Hebrides rear-arc regions.