Current therapy of patients with appendiceal abscess or phlegmon is in evolution. Controversial areas include initial conservative therapy, drainage of periappendiceal abscesses, and the role of interval appendectomy. To evaluate the safety and efficacy of conservative therapy and of interval laparoscopic appendectomy (ILA). Patients with signs and symptoms of acute appendicitis and a palpable right lower quadrant mass were included. Abscess/phlegmon was documented with ultrasound or computerized tomography. After initial therapy with antibiotics, patients were discharged to home. ILA was performed 6 to 12 weeks later. Twelve patients were included. Four patients had phlegmonous appendicitis and eight had an abscess, but only four had percutaneous drainage. All patients improved without surgical exploration and were subjected to ILA. ILA was successful in 11 of 12 patients; a median hospital postoperative stay of 1 day was required, and no perioperative morbidity was encountered. All patients returned to routine activities within 2 weeks of surgery. 1) Initial conservative management of patients with appendiceal abscess/phlegmon is prudent, safe, and effective. 2) Interval laparoscopic appendectomy can be performed safely and effectively.