Acute appendicitis is a common cause of acute abdomen requiring an emergency appendicectomy. Complications such as perforation and peritoneal contamination leading to peritonitis can result from delay in presentation and an emergency operation. This study prospectively recruited 101 patients diagnosed with acute appendicitis to correlate the bacterial flora with the severity of appendicitis. The results show that 90 patients had acutely inflamed or gangrenous appendicitis and 11 had perforated appendicitis. The ages ranged from 6 to 49 years with a median of 20 years. There were 59 females and 42 males. The commonest isolates were aerobic bacteria such as Escherichia coli, Group D streptococci and Klebsiella pneumoniae. Mixed infection with anaerobes such as Bacteroides fragilis was seen only in perforated appendicitis. The best choices of antibiotic were a fluoroquinolone, cephalosporin and aminoglycoside for aerobic organisms and metronidazole for anaerobes.