Patients with Acquired Immunodeficiency Syndrome (AIDS) may present acute abdomen with modified clinical manifestations which may lead to errors and delays in preoperative diagnosis, with frequent delays in treatment. OBJECTIVE To study clinical signs, diagnostic criteria, etiology, surgical management and mortality in patients with AIDS submitted to exploratory laparotomy. METHODS We reviewed the records of thirty-one AIDS patients admitted in the period 1986-1993 at the Emergency Surgical Service--Hospital das Clínicas, University of São Paulo submitted to exploratory celiotomy due to acute abdome. RESULTS Abdominal pain was the most frequent symptom and the diagnosis of acute abdome was made based upon physical examination, laboratory tests and imaging techniques. Gastrointestinal tract perforation was the most frequent cause of acute abdome, mainly due to Cytomegalovírus infection. All patients presented postoperative complication, specially wound infection. Mortality rate was 42% due to sepsis and multiple organ failure. CONCLUSIONS Based upon these data we conclude that: AIDS patients usually present masked clinical signs of acute abdomen; stomas should be formally indicated. Mortality is extremely high due to immunocompromised state, delayed diagnosis and treatment and non therapeutic celiotomies.