['To evaluate the effect of locally applied tranexamic acid on postoperative blood loss and measures of fibrinolysis in drained blood.', 'Prospective study.', 'University hospital, Norway.', '30 patients operated on for low back pain by screw fixation of the lumbar spine, 16 of who were randomised to be given topical tranexamic acid.', 'Postoperative blood loss after 18 hours. Concentrations of plasmin/alpha2-antiplasmin (PAP) and D-dimer in arterial and drained blood at the time of wound closure and in drained blood after 1 hour.', 'In the tranexamic group median (interquartile) blood loss was reduced by half from 525 (325-750) ml to 252 (127-465) ml, p = 0.02. In drained blood after one hour the increase in the concentration of PAP was 150 (109-170)% and D-dimer 150 (107-272)% in the tranexamic group compared with the control group where the increase in PAP was 320 (140-540)% and D-dimer 260 (161-670)%.'] Does tranexamic acid given into the wound reduce postoperative blood loss by half in major orthopaedic surgery?