The impact explanation for the Cretaceous-Tertiary (KT) boundary mass extinction has received much support and confirmation, although it continues to be challenged. As part of the ongoing study of this problem by many scientists worldwide, two lines of investigation are proposed: (1) detailed stratigraphic study of the sequence of events during the boundary crisis, and (2) search for an impact crater on oceanic crust by studying possible tsunami effects on continental slopes and margins. (1) The stratigraphic study will use numerous Apennine KT boundary sections deposited near the CCD, which are sensitive to paleoceanographic changes. Recent work shows that abnormal reducing and corrosive conditions resulted from the KT event in this environment, and the character and duration of these events, and their relation to fluctuations in the iridium profile and the occurrence of impact signatures will be examined. (2) Recent work by others strongly suggests impact in the Southern U.S. -Caribbean-Gulf of Mexico area. Work on sections proximal to the impact site will yield detailed understanding of the impact event.