The N1-acetylderivatives (ASA) of sulphanylamides (SA) were prepared and their stability to hydrolysis was evaluated together with the spectroscopic and antibacteric activity parameters, with the aim both of obtaining electronic structure-activity relationships and of comparing these results with those previously found for SA. From our results it appears that: a) the stability to hydrolysis is dramatically reduced on passing from the aqueous medium (pH 7) to the culture broth, and that b) in general, the ASA examined do not show any greater antibacterial activity with respect to the parent compounds, as suggested by the values of the spectroscopic indices-taken as experimental electronic indices. This result is in full agreement with the structure-activity relationships previously proposed fo the sulpha drugs.