This study is aimed at investigating the etiology and clinical characteristics of mesenteric adenitis in Korean adults, prospectively. Clinical manifestations of fifteen patients who presented with the acute onset of right lower quadrant pain and sonographically enlarged mesenteric lymph nodes and normal appendix were evaluated. For etiologic diagnosis, stool culture, serologic test for Epstein-Barr virus, and Widal test were performed. Colonoscopy with mucosal biopsies and microbial tissue cultures were performed in 12 of 15 patients. Of fifteen patients 6 were male and the average age was 29.9 (17 approximately 41) years. Associated symptoms were diarrhea (80%), fever (73%), nausea and vomiting (27%). Right lower quadrant tenderness was observed in all cases but rebound tenderness was observed only in 26.7% of the cases. Etiology was identified in 7 cases (47%): 2 Yersinia enterocolitica infection, 2 non-typhoidal Salmonella infection, 2 tuberculosis, and 1 typhoid fever. In colonoscopic examination, signs of active inflammation were observed in 9 cases (75%) and inactive or normal findings in 3 cases (25%). All of our patients, except for the patients with tuberculosis and typhoid fever who needed specific antibiotic therapy, improved spontaneously without using antibiotics. In conclusion, the etiology of mesenteric adenitis in Korean adults seems to be different from that of western countries. Furthermore, mesenteric adenitis in Korean adults is a clinical syndrome, frequently found in a relatively young age group, which improves spontaneously unless specific anti-microbial agents are indicated by microbiological tests, such as tuberculosis or typhoid fever.