Benedetto Antelami was the sculptor and probably also the architect of the Baptistry of Parma at which he worked from 1196 to 1216. The study of the polychromy of this monument is very important in the history of Romanesque and Gothic sculpture in Europe because the complex relationship between monumental stone sculpture and polychromy is still largely based on pure hypotheses. A thorough program of scientific research has been carried out at the Baptistry. The origin, nature, physical properties and state of conservation of the stones are studied. Their treatment with the acrylic/silicone mixture of Paraloid B-72/DriFilm 104 is described and assessed. The components of a number of paint samples were analyzed using a scanning electron microscope connected to an energy dispersive analytical system. The results obtained give information on materials and techniques which is presented in a summary form. The conservation work undertaken is briefly described. Some preliminary conclusions about the geographical extent and historic significance of polychromy on Romanesque and Gothic stone sculpture are indicated.