Background. The Italian Society for Thrombosis and Haemostasis (SISET: Società Italiana per lo Studio dell'Emostasi e Trombosi) promoted the development of a series of guidelines which would adopt evidence-based medicine methodology on clinically relevant problems in the field of haemostasis and thrombosis1. The objective of the present guidelines is to provide recommendations for the pre-operative and pre-procedural assessment of the bleeding risk with the aim of reducing the incidence of preventable bleeding complications and limiting laboratory tests to the bare necessary. The risk of bleeding is usually assessed by eliciting the personal and family history for abnormal bleedings, and performing laboratory tests that explore the haemostatic functions. These laboratory tests generally include the prothrombin time (PT), the activated partial thromboplastin time (APTT), the platelet count, the bleeding time and, more rarely, PFA-100 closure time, thromboelastography and platelet aggregation tests. However, the choice and interpretation of these tests and the clinical management of patients with abnormal results is highly variable. The appropriate choice of laboratory tests requires an accurate assessment of the clinical situation, the evaluation of the prevalence of bleeding disorders, the test characteristics, the cost and the consequences of false-positive and false-negative results. Methods. A multidisciplinary working group (MWG) was involved in the definition of relevant clinical questions. The specific clinical questions to be answered by the guideline were formatted by using the PICO template, in order to optimize the subsequent steps of literature search and recommendation issuing. A systematic literature search was conducted and the each selected reference was assigned a proposed evidence level score accordingly to the Scottish Intercollegiate Guideline Network scheme (SIGN). For each clinical question the MWG produced a "weighted judgments". For questions without any definitive answer in the literature (absence of evidence, evidence of low quality and/ or contradictory), the MWG used a formal consensus method (RAND methodology) to anyway issue a clinical recommendation (these were always scored as D - expert opinion consensus). Results. The predictive value of haemostatic tests for bleeding complications after surgery or invasive procedures has been evaluated in prospective or retrospective cohort studies only. No randomized studies are available. All retrieved studies were of low methodological quality with a high potential for bias because none conducted a blinded outcome assessment. In addition, different criteria for the severity of bleeding events and different reference values of the laboratory tests were adopted. The low methodological quality limits the validity of the results of these studies. Some of the clinical queries proposed by the working group were not addressed by the studies available in the literature. The areas with evidence, although of low quality, are the following: general surgery in adults (for history, PT, APTT, platelet count and bleeding time), neurosurgery in adults (for medical history, PT, APTT, platelet count), adenotonsillectomy in children (for history, PT, APTT, platelet count and bleeding time), invasive procedures in adults (for PT, APTT, platelet count), dental extractions (for the bleeding time only), cataract extraction (for platelet count). No studies are available for major surgery other than adenotonsillectomy in children, neurosurgery in children and invasive procedures in children. 1. All recommendations by the MWG are of grade D. The following criteria were considered for each consensus: necessity of a baseline value in case of subsequent unexpected abnormal bleeding, legal implications and cost-benefit evaluation. 2. The MWG recommended that a detailed personal and family history for bleeding, preferably with locally designed structured questionnaires, and physical examination should be considered good practice procedures before any surgical or invasive int rvention. 3. The MWG consistently recommended that PT, APTT and platelet count should be performed routinely before surgery or invasive procedures (except for diagnostic endoscopies) both in adults and children even in case of a negative history of bleeding. This recommendation differs from those of previously published guidelines which did not recommend preoperative haemostatic tests in subjects with a negative history of bleeding, although with a grade C2-4. The MWG of this guideline ascribed a relatively higher value to preventing bleeding events and medico-legal problems and a relatively limited value to cost which is low for PT, APTT and platelet count in Italy. 4. The MWG consistently recommended that the bleeding time, plasma fibrinogen, PFA -100, thromboelastography and platelet aggregation tests should not be performed routinely before surgery or invasive procedures either in adults or children with a negative history of bleeding.