In 1975 and following years, about 4,000 perfectly preserved flint implements were collected over an area of about 5,000 m2 (called "site B"), near Maccarese (locality "Le Cerquete"), on the coastal area of Rome in central Italy. The implements have been dated back to Middle and Upper Palaeolithic times, their age ranging from the isotopie substage 5a to the end of Pleistocene. During excavations carried out in 1991, a sharp decrease in number of implements was noticed immediately below the ground surface. The soil in which the lithic industry was found, has been classified as a well developed Chromic Luvisol, which is thus certainly not recent. Moreover, we know that there are at least two sedimentary cycles in the evolution of the Maccarese plain, the oldest of them dating 90,000-÷50,000 years B.P. The deposits of this cycle are cut seawards by a scarp outlining a terrace developed between 5 and 12 m a.s.l. The terrace is formed of two partions on the basis of pedologie evidence. The younger sedimentary cycle is related to the Versilian transgression (of Holocene age) with deposits outcropping 2 m a.s.l. The area where the Chromic Luvisol outcrops, has a limited extent and a regular form corresponding to the concentration of lithic implements on the ground surface. It is concluded that the area of maximum concentration of artefacts is not the part that has left of an archaeological living floor, rather it is a typical example of artefacts concentration due to small scale natural phenomena.