Between 5th November and 17th December 2001, a geophysical survey was undertaken at Ostia Antica, by Southampton University and the British School at Rome, on behalf of the Deutsches Archäologisches Institut and the American Academy at Rome. The geophysical survey at Ostia was successful in locating and mapping archaeological remains in areas within and associated with the Roman city. To the north of the excavations, structures were located associated with the harbour and river port of the town, and the ancient course of the Tiber, although the actual course of the river was not unequivocally located. Survey within the excavations clarified the nature of ground adjacent to the theatre and Piazza delle corporazioni, and a number of other _insulae_ were found outside the walls of Region IV, and in Region V. The results were most successful outside of the excavations to the south, around the Via Laurentina and villa, demonstrating the full extent of the archaeological remains across the area including access to the city, tombs, and buildings pre-dating and associated with the villa.