During the first part of 1973, two tests of seismic energy transmission from the Pacific oceanic shelf and adjacent plate to continent using controlled sources were carried out in dissimilar areas, one associated with Colombia and one associated with Peru. Results from both experiments show that the energy transmission as far inland as the eastern cordillera is surprisingly good, unlike our experience in the Andes shooting parallel to structure. Since the differences in the degree of tectonic activity and differences in structure inferred from geology, bathymetry, gravity and seismic natural event information for these two regions spans that found in western South America, it is believed that these results are sufficiently general to imply that the whole of western South America can be studied using ocean shot points. Copyright 1975 by the American Geophysical Union.