Jalaawi W¹, Adlan H², Mostafa H³. ¹ Researcher of dental public and preventive dentistry.Faculty of Dentistry.Mansoura University. ²  Professor of dental public and preventive dentistry. Faculty of Dentistry.Mansoura University. ³ Associate of dental public and preventive dentistry. Faculty of Dentistry.Mansoura University. Abstract: Objectives:halitosis is offensive odor to others so that we undertook this study to assess the prevalence of halitosis and to investigate the oral and systemic associated risk factors with halitosis among a group of medically compromised patients. Methods:2000 of medically compromised patients were involved in the study, their ages ranged from 16-60years.Organoleptic scoring assessment, WHO DMFT index (1997),WHO basic periodontal disease index(1977) were recorded. Questionnaires were used to obtain past medical history . Results:There were 698 patients (34.9%) of the examined patients suffering from different degree of halitosis. Oral malodor was significantly related to old age ,low educational level(p < 0.05), oral causes as [tongue coating, tonsillitis, lip and palatal ulcers(p < 0.05)],WHO1997 DMFT index and WHO 1977 periodontal index(p < 0.05),oral hygiene measures[time of brushing/day ,mode of flossing(p < 0.05)] oral intake[dietary intake ,snacks causing halitosis (p < 0.05)]medications[number and type of medicaments(p < 0.05)] systemic diseases[diabetes mellitus145 patients(20.8%) was higher percentage  of other systemic diseases and (p value<0.05 and sinusitis(p < 0.00). Conclusions:halitosis is prevalent with high degrees among patients who are old age      ( 46-60years) males with lower educational level,live in rural area had tonguecoating ,tonsillitis,advanced periodontitis, High DMFT index with mean17.45,not flossing or vigorously floss their teeth,eating and drinking diet causing halitosis with snacks more than one time daily,taking drugs more than 3types and suffering from diabetes mellitus  and sinusitis had high scores of halitosis.