230Th/234U dating of speleothems from southeastern Australia documents changes in effective precipitation over the past 500 k.y. at a temporal resolution not previously achieved. Results show that the highest effective precipitation for the southeastern interior of Australia occurred during stadials and cool interstadials of the past four glacial cycles. Interglacials and warm interstadials, as well as glacial maxima, are comparatively arid. We suggest that lower regional temperatures over the continent and changes in atmospheric circulation (stronger Walker circulation) produced the observed periods of increased effective precipitation.