A booklet published from notes given to the participants for the post graduate course on the conservation of monuments organized by the University of Rome and ICCROM. After briefly describing the main problems caused by humidity, five case studies of damp buildings in Italy (Santa Maria della Rotonda in Albano, Palazzo Civico di Siena, Cripta di San Colombano nell’Abbazia di Bobbio, a villa in the Roman countryside, and the Palazzo dell’Accademia di San Luca a Roma) are presented with diagnosis treatment used and rehabilitation work. Numerous figures illustrate the case studies.