The pre-late Paleozoic basement complex of nuclear Central America is exposed in an arcuate zone that extends from the Caribbean Sea to Chiapas, Mexico. The trend of this arc parallels fold trends in younger sedimentary rocks on both sides of the arc, which has led to the widespread, previously unsubstantiated assumption that structural trends in the ancestral orogenic zone also form an arcuate regional pattern. Analysis of structural and lithologic trends in five areas of this arc indicates that the pre-late Paleozoic ancestral orogenic zone has undergone two phases of penetrative deformation. Folds of the first phase, which was most intense, are oriented parallel with the arc, as suspected, whereas folds of the second phase have north-trending vertical axial planes. The distribution of lithologies in the orogenic zone suggests that the premetamorphic provenance was the widespread Precambrian terrane of southern Mexico. The angular relationship of basement complex structural trends on opposite sides of the Cuilco-Chixoy-Polochic fault zone, which appears to be the most likely boundary between the Americas and Caribbean plates during Cenozoic time, limits left-lateral offset along this zone to less than 150 km.