Mechanical Intestinal Obstruction is a serious surgical condition that requires urgent surgical attention. This study was carried out in Aba, Abia State, using the Abia State University Teaching Hospital (ABSUTH) and three private Hospitals; Manaratha Specialist Hospital, Nnenna Hospital Limited and Ebony Hospital Limited. The study was designed to determine the pattern and prognostic factors in Mechanical Intestinal Obstruction (MIO) in Adults in Aba. It was a one (1) year prospective study from May 2004 to April 2005. Adult patients of both sexes admitted with MIO in the four centres were included in the study. A total of 104 patients were studied. The mean age was 49.5 years. The male: female ratio was 1.8:1. Obstructed external abdominal wall hernias were the commonest cause of MIO, occurring in 67 patients (64.4%). Abdominal pains, vomiting, abdominal distension and constipation were the commonest presenting symptoms. Ten patients (9.6%) were successfully treated conservatively while 94 patients (90.4%) had operative treatment. Strangulation of the bowel was the major indication for resection. The commonest post-operative complication was wound infection, which occurred in 16% of the patients. A mortality rate of 10.6% was recorded. Significant prognostic factors which affected outcome in this study were duration of symptoms before presentation and the time interval between presentation and surgical intervention. The pulse rate on admission, total white blood cell count (WBC), serum potassium and sodium concentration before surgical intervention also significantly affected outcome. Cause of obstruction, site of obstruction, and surgical procedure carried out were other significant prognostic factors. The high incidence of external abdominal wall hernia as a cause of MIO in adults and the attendant mortality of 10.6% indicates that MIO is still a problem to the surgeon in Aba. There is the need to promote increased public awareness on the magnitude of the problem. Patients should be encouraged to present early to hospital, and adequate and affordable management instituted. This will help to reduce the morbidity and mortality associated with MIO.