This paper describes a survey of rural sites located around the Roman colony of Cosa (founded 273 B.C.). One hundred and thirty-two sites were mapped and for the most part dated; the results allow a reconstruction of the settlement history of rural Cosa. The area apparently had sparse habitation before the Roman period, a steady population during the Republic, and a decline under the Empire which left a sparse population by the 4th century AC. The categorizing of the sites by size shows a concentration of the largest sites in the shore area and medium and small sites elsewhere. The results are compared with those of other comparable surveys undertaken in Italy.