A study of two principal pollutants (sulphur dioxide and hydrochloric acid) on the deterioration of stone. These two agents can directly or indirectly set off a reaction involving substances which accelerate deterioration. During a year-long study, samples were taken from a building in the center of Venice. The author presents the monthly average results and the annual histograms of the concentrations of the hydrochloric acid and of the oxides of sulphur. This study is compared to the one conducted in Florida by Junge. F.P. -- AATA