How are continental collisional orogens preconditioned by tectonic processes that operate along convergent margins prior to the collisional events? The Tibetan plateau, which is generally accepted as the archetype of collisional orogens, is a perfect natural laboratory to study this question because it contains a record of pre-collisional, Andean-style arc-related tectonics as well as collisional tectonics during the Cenozoic. General models for Tibetan Plateau evolution begin with assumptions of initial conditions for crustal thickness and mantle structure that strongly influence the results of the models. However, geological support for these assumptions is scarce. This study is integrating geologic mapping and structural, stratigraphic, sedimentologic, and geochronologic studies of widely exposed Cretaceous and earliest Tertiary basin fill and igneous rocks in the Lhasa terrane of southern Tibet to provide new constraints on the pre-collisional history of strain, basin development, paleogeography, denudation, and magmatism. It is hoped that integration of these new constraints with previous studies will lead to a unified tectonic model that provides realistic initial conditions for the lithospheric structure of southern Tibet prior to the Indo-Asian collision. The results should have broad implications for models of Cenozoic orogeny in central Asia, as well as collisional orogenesis in general.