Marine geophysical measurements off Trinidad-Tobago delineate prominent structural trends revealed in the shallow sedimentary strata. Pilar block is one of the prominent structures along the boundary between the South American continent and Caribbean plate. The block is a narrow horst bounded on the north and south by major fault zones, which apparently continue from the Araya Peninsula of Venezuela eastward to about 58°50^primeW. Structural features north and south of the Pilar block either die out at the block or veer subparallel with it. North of the block, the Barbados Ridge is an anticlinorium which shows evidence of folding and fracturing apparently as a single tectonic unit. Long-period, high-amplitude magnetic anomalies, forming a zone somewhat parallel with he Lesser Antilles arcuate trend, suggest that the prominent trends of the anticlinorium extend across the continental shelf to the Pilar block. Within the study area, the geophysical data show no evidence for extensive translation between the South American continent and the Caribbean plate in comparatively recent time.