A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed whether blood pleurodesis is effective for cessation of persistent air leak (PAL). Altogether more than 43 papers were found using the reported search, of which 10 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that autologous blood pleurodesis has superior outcomes when compared with conservative management for treatment of postoperative PAL. In addition, for PAL causing pneumothorax, blood pleurodesis [optimal volume 100 ml (from two studies)] should be considered in patients who are unsuitable for surgery, talc pleurodesis is ineffective or not viable (including cases complicated by acute respiratory distress syndrome) and a prompt resolution is required. Some 70-81% of patients treated for postoperative air leak resolved within 12 h and 95-100% within 48 h vs. a mean of 3-6.3 days (from two studies) with simple drainage. Resolution of pneumothorax with blood pleurodesis was also significantly shorter (P<0.01). Overall success rates (from all studies) were 92.7% (n=133) from patients having undergone pulmonary surgery (76.6% in one injection, n=111), and 91.7% (n=109) of patients with pneumothorax. Recurrence rates were between 0 and 29% compared with 35-41% for simple drainage, although one controlled study in which the recurrence rate was improved from 16% in controls to 0% in the blood pleurodesis group (at 12-48 months). Minor complication (empyema/fever/pleural effusion) rates varied between studies (0-18%), although they show reduced incidence in line with improving technique over time. A controlled study looking at acute respiratory distress syndrome complicated by pneumothorax showed a significant reduction in mortality (odds ratio 0.6), time to cessation of air leak (P<0.01), weaning time (P<0.01) and intensive treatment unit (ITU) stay (P<0.01) whilst another randomized control study showed significant reduction in hospital stay following pulmonary resection (P<0.001).