Both, the formation of aeolian dunes and the rate of sand transport in arid environments are controlled by the wind regime. The Sistan region in eastern Iran and the Registan region in Southwestern Afghanistan are strongly influenced by the wind of 120 days (Sadobist Roozeh wind), which is blowing along the Iran-Afghanistan border from North to South, then shifts it's direction toward the Southeast into the Sistan region and, finally, continues eastward into southwestern Afghanistan, forming the Registan sand seas. It blows during the hot season due to the pressure gradient between the Turkmenistan high and the Pakistan Low. In order to determine the wind regime and the sand transport, wind roses based on long-term datasets from 16 meteorological stations, the Drift Potential (DP), the Resultant Drift Direction (RDD), the Resultant Drift Potential (RDP) and the RDP/DP ratio have been calculated using the Fryberger (1979) method. The distribution of the Registan sand dunes was surveyed by using Landsat ETM data, Google Earth scenes and field operations (the latter only in the Iranian part). The spatial differences of the drift potential were also mapped using GIS and geostatistical methods overlaying the sand dune map. The results show that the drift potential (DP) increases from north to south along the border between Iran and Afghanistan and reaches to highest values in the Sistan region, then decreases gradually in the Registan sand seas. The highest wind energy, based on DP matches, was determined exactly where the ephemeral lakes in the northern part of the Sistan plain are located, which function as a source area of intense dust and sand storms during the dry season. The temporal trend of the DP showed an increase between 1999 and 2007, followed by a decrease until 2015 in Sistan. The results show that the wind regime in the Sistan and Registan regions is unimodal during the wind of 120 days (the Sadobist Roozeh) period, which is also supported by the dominance of transverse, barchanoid and barchans dunes in both regions.