During the period from April 1973 to June 1975, 31 cases of palpable mass on the right lower abdoma in adulthave been observed at Korea General Hospital for determining basic type of mass site or origin, age incidence,sign and symptoms as well as radiological findings. The results obtained are as follows : 1. The disease is morecommon in males than females, with 1.8:1 ratio. Peak age incidence of palpable mass on the right lower abdomen is4-5th decades. 2. The most frequent complaint of palpable mass is localized abdominal pain, melena and generalizedabdominal pain are next frequent symptoms. Most of the patients with malignant tumor in the right colon andterminal ileum complained melena. 3. Thirteen cases (42%) of palpable mass on the right lower abdomen aredeveloped in less than 15 days, and adenocarcinoma was most commonest histological finding in the right colon. 4.The commonest location of palpable mass on the right lower abdomen occurs in the cecum and ascending colon. 5.Barium enema examination was the most signific-ant and useful study in the roentgenological evaluation of rightlower abdominal mass in adult. 6. The commonest lesion of palpable mass on the right lower abdomen wasadenocarcinoma of the right colon, the next common lesions were right ovarian cyst and periappendiceal abscess. 7.A case of ectopic seminoma in the terminal ileum was encountered.