Objectives: The purpose of this study was to identify the most frequently encountered predisposing factors in relation to the etiology of pericoronitis in young adults and to compare these findings with similar studies. Method and materials: The patients included in this prospective study were those presenting for treatment of signs and symptoms of pericoronitis in the mandibular third molar area during an 8-year period from 1994 to 2001. A standard check sheet of subjective and objective observations was completed, and female patients were asked about menstruation or pregnancy. Each patient with a diagnosis of pericoronitis was interviewed and observations were recorded. Patients were asked about the symptoms relating to the pericoronitis. Patients were divided into five 5-year age groups ranging from 16 to 40 years. Results: During the 8-year period, 2,151 patients presented diagnosed cases of pericoronitis; 932 (43.3%) patients were male and 1,219 (56.7%) were female. The peak age of occurrence of pericoronitis varied from 21 to 25 years (55.2% of the patients). The incidence of pericoronitis was highest in September (207 [9.6%]), followed by April (181 [8.4%]); for subacute pericoronitis, the highest was in February (128 [5.95%]) and April (112 [5.2%]), followed by October (97 [4.5%]). The most frequently seen predisposing factor was upper respiratory tract infection in 815 (37.9%) patients, followed by stress in 473 (22%) patients. Conclusion: It was concluded that the upper respiratory tract infection was the most frequently predisposing factor, which could precipitate pericoronitis.