['Prospective observational study.', 'To investigate the potential association between fibrinogen, bleeding, and transfusion requirements after scoliosis surgery.', 'Bleeding complications during and after orthopedic surgery are associated with increased morbidity and mortality. Early identification of patients with increased risk of excessive bleeding offers the possibility to initiate countermeasures. Fibrinogen is a key protein in the coagulation cascade, and thus a potential biomarker for bleeding risk.', 'A total of 82 otherwise healthy patients (mean age: 15 ± 3 years, 85% girls) undergoing surgery for adolescent idiopathic scoliosis were included in the study. Patient variables (age, gender, operation time, and thrombosis prophylaxis), preoperative laboratory variables (hemoglobin, platelet count, activated partial thromboplastin time [aPTT], prothrombin time [PT], and fibrinogen), peroperative and postoperative bleeding volume, and transfusions were registered. Correlations between laboratory variables and bleeding volume were calculated with Pearson test. Patient variables and laboratory variables were compared with Student t test between patients with bleeding volume in the upper quartile ("bleeders") and the remaining patients, and between patients with extensive transfusion (defined as >2 U of packed red cells) and no or limited transfusions (≤ 2 U).', 'Mean fibrinogen concentration was 3.0 ± 0.7 g/L (range, 1.3- 4.9). Mean total perioperative bleeding volume was 1552 ± 1019 mL (range, 100-5800 mL). Total bleeding volume correlated significantly with preoperative fibrinogen concentration (r = -0.31, P = 0.005) but neither with platelet count, aPTT, nor PT (P = 0.61, 0.46, and 0.57, respectively). Bleeders had significantly lower preoperative fibrinogen plasma concentration (2.6 ± 0.6 vs. 3.1 ± 0.6 g/L, P = 0.002). Of total, 16% (13/82) of the patients were transfused with >2 U of packed red cells. Patients with extensive transfusions had significantly lower preoperative fibrinogen plasma concentration (2.5 ± 0.7 vs. 3.1 ± 0.6 g/L, P = 0.002), while preoperative platelet count, aPTT, and PT did not differ.'] Is preoperative fibrinogen plasma concentration associated with perioperative bleeding and transfusion requirements in scoliosis surgery?