Halitosis is a term used to describe noticeably unpleasant odor exhaled in breathing. It is a general term used to describe the unpleasant breath regardless of its sources, oral or nonoral. Whereas oral malodor is the term especially used to describe the odor emanating from the oral cavity. Halitosis, which is in synonym with breath malodor, foul breath and fetor oris or simply bad breath, affects a large proportion of population, which may cause a significant social or psychological handicap to those suffering from it. Halitosis is classified on the basis of etiology and patient\'s criteria. This chapter covers the pathogenesis of oral malodor, etiology, diagnosis of halitosis, and treatment and management of oral malodor. Treatment of oral malodor is a step-by-step problem solving procedure. Before commencing the treatment, a clinician must determine the source of malodor. The simplest way to distinguish oral from nonoral origin is to compare the smell from mouth and nose.