This article is a précis of the publication of the excavations at the Roman port of Cosa in Italy now being prepared by the author and 21 specialists in various fields. The excavations were begun in 1968, following a survey in 1965 both on land and underwater. The port, presumably founded with the early Latin colony on the hill above in 273 B.C., is the earliest Roman harbor thus far known. The remains of the port are described along with its concrete masonry piers which probably date from the late 2nd or early 1st century B.C., supplying the earliest dated evidence for the use of tufo and pozzolana concrete in water.