Geoarcheological survey conducted in 1979-1980 mapped and described 87 historic-period sites in Kedah, Peninsular Malaysia. The sites include Indian-style shrines long invoked as proof of Indian domination but which actually appear to have played very peripheral roles in a Malay-controlled extraregional exchange system, which grew out of internal exchange; by the 8th Century, the first of three Kedah entrepots controlled trade with China, India, and the Middle East. A major populational shift appears to have followed the blocking of a major estuary with silts. Marked erosion upslope, probably beginning centuries earlier, produced coastal progradation throughout the area, eventually creating a vast coastal floodplain, where irrigated rice is grown today. Site locations in this dramatically-changing landscape were investigated through analyses of sediments, soils, landforms, and biotic communities. Three hypotheses were tested: (1) that the populational shift followed the infilling of the old estuary; (2) that trade sites remained closely correlated with major river drainages; and (3) that the early historic-period subsistence base was dryland agriculture. A radiocarbon date from the oldest of seven burn horizons examined in an upslope soil profile suggests that erosion here, with redeposition in the old estuary below, was well underway by A.D. 610-1020, with repeated cycles of dryland agriculture hastening the process. Tradeware finds suggest that the populational shift took place c. A.D. 1200-1250 in order to utilize a still-patent river route for trade. Every site is located beside or overlooking a current or relict waterway with access to areas rich in forest products. Massive erosion throughout the Peninsula suggests that bush/short-fallow dryland cereal agriculture supported the Malay exchange-based system until hillslope soils were exhausted. Evidence for landscape change throughout coastal Malaya is considered in the concluding chapter in an attempt to locate, by applying the geoarcheological evidence, several elusive trade-related placenames recorded by the earliest Western visitors to describe the Peninsula.