Halitosis or bad breath is a taboo subject that is a widespread problem in the general population. Causes of bad breath can be multifactorial and long time sufferers can be marred from deep psychological stress. Because nine out of ten cases have an oral cause, the initial inquiry should be with a dentist. In a retrospective study from February 2003 to February 2010, the halitosis clinic at the University of Basel analyzed data from 465 patient medical histories. Study objectives evaluated the causes of halitosis, gender distribution and treatment success. All patients reported to have suffered from bad breath. However, 82.7% were actually diagnosed as having halitosis. Within this group, 96.2% showed an oral etiology and 3.8% showed an extra-oral cause. Women suffered significantly more from psychogenic halitosis. Success rates of 92.6% subjectively and 94.5% objectively reflect the treatment success of the diagnostic and therapeutic concepts presented at the University of Basel halitosis clinic over a seven year period.