The Serranilla Key coastline variation was determined by the comparison of coastlines extracted from images and aerial photographs with different temporal resolution within a period comprised between 1944 and 2009. The Digital Shoreline Analysis System – DSAS module of ArcGIS was used to determine those variations. A reduction in the coastline perimeter from 1.994 m in 1944 to 1.872 m in 2009 was observed and the area of the Key increased from 157.720 m2 in 1944 to 125.650 m2. The erosive tendency was incremented in the period between 2007 and 2009.Key