Over 600 earthquakes that occurred in Iran between 1920 and 1972 have been relocated. The new epicentral positions delineate many active faults and seismically active tectonic zones in Iran. The Ferdows fault, the Kuhbanan fault, the Nayband fault, various segments of the Shahrud fault, and a fault off the Coast of Makran are seismically active; there are other seismic trends which are not clearly related to corresponding surface faults. The Zagros thrust separates a more active folded series from the rest of Iran. The folded series of the Zagros itself shows various seismicity levels and is thus divided into several seismotectonic provinces. Older Arabian north-south trends in some areas of the folded series are marked by subcrustal earthquakes. The east-west trend near Lar consists of crustal earthquakes. The epicentral locations present a generally diffuse pattern, best explained in terms of relative motions between the Arabian plate and the Persian plate. The relocated epicenters, together with geological information, regional geomorphology, distribution of salt domes, structural trends, and active faults, are used to construct a seismotectonic map of Iran which includes 23 seismotectonic provinces. The seismicity and boundaries of each province are discussed.