We monitored 48 patients, considering ECG, Oxygen Saturation and arterial pressure. Our aim was to evaluate the incidence of cardiovascular and respiratory complications of colonoscopy. In 40% of the cases, these parameters showed significant modifications and in 9 cases (19%), patients showed cardiovascular events to such an extent as to constitute a potential life-threatening situation. These cardiovascular events were in relation statistically significant with pre-existing cardiovascular pathology, COLD and hypoxia. Hypoxia, in turn, depended almost exclusively on i.v. sedation, and returned to normal values when the patient received oxygen. In most cases, events were not correlated to any specific symptom. This study demonstrated a rate of cardiovascular complications higher than previous retrospective analyses would lead one to believe. We recognize the value of accurate history-taking and have adopted its use in selecting high risk patients before colonoscopy, especially if sedation is contemplated.