Recent intensive investigations in the Antigua Valley of the central highlands of Guatemala reveal Late Classic regional cultural variation. Defensive features and settlement patterns indicate that the control of territory, if not actually its defense, was important during the period. Ceramic comparisons and sculptural analyses demonstrate external contacts with other parts of the highlands and the Pacific piedmont. Climatic change may explain the decline in population at the end of the period in the Antigua Valley. This chapter highlights the regionalization of highland cultures and suggests that a cultural boundary existed in the Antigua Valley, contributing to the ongoing discussion of the Late Classic Maya.