The Peruacu valley presents an exceptional concentration of speleologial and archaeological sites with rock art. The rock art, executed in cave entrances and in rock shelters, is undergoing progressive degradation, as observable through time, mainly during the last 15 years. The purpose of this study was to collect and document data related to the deterioration processes, in order to contribute to a better understanding of the decay processes and, in the future, to the formulation of the site management policies. For this study, the Janelao North shelter was selected, and minute samples were collected for identification of pigments and predominant degradation products. The main alterations observed were fading of paintings, flaking of the rock surface and pictorial layer, lixiviation, exfoliation and erosion of the superficial layer, salt efflorescence and deposits, humidity stains, micro-organic growth, animal activity (presence of nests and excrement) and dust.