BACKGROUND Nonagenarian population is growing, and so is the number of them needing emergency surgery. Yet, their treatment is often based on the outcomes of younger patients: although old age is known to be a risk factor for surgery, its level is not clear. This is a prospective, observational study to describe the population. It is aimed at providing quantified scientific evidence of the current procedures and their outcomes. METHODS All non-traumatic nonagenarians who underwent surgery between July 2006 and September 2010 in our University Hospital were recruited and followed up over a month after discharge. A descriptive statistical analysis was performed. RESULTS Of the approximately 12 660 surgical emergencies, 102 were nonagenarians: 69.6% were women, who mostly had an ASA score III (62.7%). Perioperative morbidity and mortality rates of 61.6% [95% confidence interval (CI): 52.33-71.19%] and 35.3% (95% CI: 26.01-44.57%), respectively, were found statistically associated with preoperative neoplasms. The most frequent causes of surgery were acute limb arterial thrombosis (20), incarcerated hernia (17), and bowel occlusion (14). Confusion, renal failure, and abdominal problems accounted for the most frequent causes of morbidity. Among them, abdominal complications, cardiogenic pulmonary oedema, aspiration, stroke, and renal failure were associated with mortality. CONCLUSIONS The study gave scientific support and actual figures to many intuitive beliefs: morbidity and mortality are high and are associated with many preoperative comorbidities. All this, combined with an already reduced life expectancy, and a presumably low physiological reserve makes these patients particularly vulnerable to emergency surgery.