Aztreonam is the first monobactam and is unique among beta-lactam antibiotics for its spectrum of activity that is exclusively active against gram-negative aerobic bacteria. Broad clinical experience with this agent supports its use in the treatment of adults with severe or complicated urologic infections. Aztreonam may be safely used in patients with penicillin allergy. With a spectrum of activity that is comparable to the aminoglycosides but without the potential for ototoxicity or nephrotoxicity, aztreonam represents a rational choice of therapy for treatment of systemic urinary tract infections due to susceptible organisms.