Tide-gauge records from southern Mexico, the Caribbean Islands, and Central and South America that span the interval 1940–1970 reveal long-term changes of relative sea level according to regression analysis and eigenanalysis. The results indicate such large variations in both direction and rate of secular movement as to rule out changes in volume of ocean water as being more than a subordinate factor. The only satisfactory explanation is that the land level beneath the tide gauges is rising in some places and sinking in others. Complex spatial patterns of relative seal-level change in southern Mexico and the Caribbean mirror the tectonic regime of these regions, exhibiting both submergence and emergence of the land. Central American tide-gauge records similarly show considerable complexity, responding to relative movement along plate boundaries. The Pacific coast of South America appears to correlate with the depth of the Benioff zone; subduction of aseismic ridges produces local highs in the Benioff zone, flanked by troughs at either side. Near the Benioff highs, relative land level is rising; between these ridges relative land level is falling. Sea-level trends in southern and Atlantic coasts of South America are closely linked with continental crustal rifting and subsidence. Data do not allow unambiguous separation of changes in ocean level from changes in land level, and no simple eustatic ocean level change can be estimated accurately from these data.