Clinical effectiveness of Aztreonam was studied. This new monobactam antimicrobial agent was tasted in the treatment of post-operative infectious complications of cardiac surgical sternal wounds. Ten patients (4 men and 6 women, age range 20 to 68 years) were entered into the study. All had a Pseudomonas aeruginosa infection of sternum or sternum and ribs and all underwent an extensive regional surgery of the infection wound and received a topical and/or IV treatment with Aztreonam. In all cases we obtained a satisfactory result, with complete eradication of the infection. Both local and systemic tolerance to the drug were excellent and no side-effect was registered. Therefore Aztreonam can be considered an active and safe antibiotic for the treatment of sternal and/or costal postsurgical infections by Pseudomonas aeruginosa.