Windcatchers are built on the roofs of houses of hot areas of the Middle East to ameliorate the internal summer climate. The archaeological and historical record shows them to have been used since antiquity, and although they are still widely found in the region today, and regularly mentioned in the modern works on architecture o-f the region, no detailed study of their types or operation has been published. Rather architects refer continually to an accepted stereotype of their form and performance on which modern architects have to rely as a design model. This study makes an original contribution to the published record. In it the badgirs, or windcatchers of a single region, Yazd, on the Persian plateau, are described; and the distribution o-f their types in the villages of the area, and city of Yazd are reviewed in relation to the climatic and historical influences on their design and use. The functions o-F badgirs in the houses of Yazd, as airconditioners and ventilators, are investigated. General temperature limits o-F their summer performance in the context of the life-style of the Yazdi, are established and reviewed in relation to comfort and the physiology of the human body and the climatic results used to interpret the distribution of windcatchers types in the wider area of the Middle East. The research provides a unique historical record of the badgirs of Yazd, illuminates the complexity of the climatic and historical influences in their distribution, and, through analysis of their performance, provides a general climatic guide that may assist contemporary designers wishing to incorporate windcatchers in modern houses in hot areas.