The Domus of Cupid and Psyche is perhaps one of the most interesting and attractive ruins in ancient Ostia.' It was excavated in 1938, but due to the Second World War it was not published until ten years later when Professor Giovanni Becatti included it in his introductory article on the Ostian mansions of the later Empire.2 Although the structure has subsequently become so well known that it is now used as an example in general handbooks,3 it has never been the subject of a specialized study. The present article seeks to remedy this deficiency.4 Like many of the buildings of the later Empire in Ostia, the Domus of Cupid and Psyche incorporated large parts of a preexisting tenement,5 which partially determined the form of the later Domus. Accordingly, the surviving remains of that apartment house together with a tentative restoration of its plan will be considered first. Then the existing ruins of the Domus will be examined and an attempt will be made to arrive at a plausible reconstruction of the building. Because the upper storey has disappeared, and the excavation reports are no longer available, its restoration will be, quite obviously, conjectural in detail.' Still, such a reconstruction allows the Domus to be viewed not as a confusing set of ruins, but as an architectural and artistic whole. In addition, careful study of the ancient form of the building suggests certain implications concerning both population patterns and techniques of design and construction in the Ostia of the later Empire. The apartment house which was subsequently transformed into the Domus of Cupid and Psyche (I,xiv,5) shared a party wall with the structure to the north (I,xiv,6), itself built only five years earlier.7 On the other three sides, the building was bounded by streets: to the east, the Via del Tempio d'Ercole; to the south, the Vicolo delle Terme di Buticosus; and to the east, an unnamed road. When the Domus was constructed, the latter street became a small piazza formed by removing the east wall of the apartment house for nearly three-quarters of its original extent (pl. 33, figs. I and 2). The best preserved section of the tenement is made up of the three shops which became the west wing of the Domus. They were originally protected by a portico, which was closed after the Domus was built in order to expand the shops.8 A stair (b) adjacent to shop a led above the ground floor areas a, m, n, o to what was either one four-room apart-