Halitosis is a common problem among humans. The cause can be oral or non-oral. Psychological causes (psychosomatic halitosis) are to be ranked as exceptional. During a period of 18 months, 144 patients were examined and treated at the Halitosis-Consultation at the University of Basle. All patients were convinced that they suffered from bad oral breath. A specially developed questionnaire was followed by a dental examination and a diagnosis. When halitosis with an oral cause was diagnosed an exclusive cause-related therapy was initiated and regulary controlled. 84% of the patients had halitosis with an oral cause; non-oral causes were rare; 12.5% (n=18) had psychosomatic halitosis. Tongue coating, gingivitis and periodontitis were the most frequent oral causes, tonsillitis the most frequent non-oral cause. No correlations were found between smoking and halitosis, or stress and halitosis. Patients with psychosomatic halitosis had a significantly higher rate of antidepressants intake. These patients generally assessed their bad breath as very strong and omnipresent. Medical examinations and treatments carried out earlier showed that the assumption of doctors, dentists and patients that halitosis was mainly caused by gastroenterological disorders, is still widely spread. The positive results of 91.9% (objective) and 96.9% (subjective) confirmed the therapeutical concept of the "halitosis-consultation" at the University of Basle as highly successful.