The supercontinent Pangaea, which existed from Late Carboniferous through about Middle Jurassic time had a unique and extreme climate, which is predicted to have been a strong monsoonal circulation that reached a maximum during the Triassic. A monsoonal climate would be expected to have had the following features: (1) dry or seasonally dry continental interiors; (2) evidence of strong seasonality, especially in low latitudes; (3) equatorial region that is dry, especially in the east; (4) maximum expression of these features in the Triassic. For the purpose of testing the monsoon and alternative hypotheses, data on paleoclimatic indicators will be compiled from the literature and data maps will be constructed for three times during the Pangaean interval that have been identified as likely to have been key times in the development of the monsoonal circulation. Particular attention will be paid to the problems of quality control on data and on the heretofore intractable problems of quantitative analysis for terrestrial paleoclimatic data. Preliminary applications of a numerical climate model to the Pangaean paleogeography will be carried out. This research will contribute to paleoclimatology and to our understanding of climate dynamics by (1) establishing a method for quantitative paleoclimatic data analysis; (2) documenting the effects of a large land mass on global climate; (3) increasing understanding of the dynamics and structure of an extreme paleoclimatic state.