Halitosis is a widespread problem but it continues to be a taboo subject. For affected patients, the dentist is often their first contact. Finding and quantifying halitosis initially serves to objectify it and look for the cause but also enables treatment to be monitored. The cause of halitosis is usually intraoral so that instituting appropriate treatment measures is the dentist's responsibility. Besides the simple organoleptic measurement of halitosis, which can be performed without any equipment, various devices are available on the market that allow sophisticated analysis of expired air by measuring and quantifying volatile sulphur compounds.