Geographic variations in the concentration of Australasian microtektites in 42 cores from the Indian Ocean, western equatorial Pacific Ocean, and the Philippine, Celebes, and Sulo Seas were used to predict the location of the Australasian tektite source crater and to estimate its size. The location that seems to best explain the geographic variations in microtekite concentrations is located in central Cambodia at about 12 ¿N latitude and 106 ¿E longitude. The diameter of the source crater is estimated to be between 32 and 114 km based on thickness of the microtektite layer at each site and distance from the predicted source area in Cambodia. The large range in estimated size of the source crater is due to a lack of knowledge about the value of the exponent that describes the radial decrease in ejecta thickness. Additional microtektite/ejecta-bearing sites closer to the source region could help resolve this problem. ¿ American Geophysical Union 1994