These paintings are located in the Ducal Palace, Mantua, Italy. To document their state of deterioration in the mid-1970's, a thorough photographic investigation was carried out. This was followed by the investigation necessary to explain the causes of decay: water vapor on the surfaces was discovered to be the main one, with the added influences of heat, air circulation, air pollution and others. The results of the analysis of the cleaning methods used so far have proven useful but not conclusive. Diagrams present horizontal cross-sections of the air temperature and RH within the chamber taken six times a day. The specialists who carried on these studies concluded that the greatest risk of damage is due to the massive influx of visitors during certain times of the year. There have already been attempts to regulate access to the chamber. It will now be necessary to determine whether these measures are sufficient. Acknowledgements are appended.