The hemostatic effect of tranexamic acid solution (4.8%) used as a mouthwash was compared with a placebo solution in 93 patients on continuous, unchanged, oral anticoagulant treatment undergoing oral surgery. The investigation was a randomized, double-blind, placebo-controlled, multicenter study. Before suturing, the surgically treated region was irrigated with 10 mL of tranexamic acid (46 patients) or placebo (47 patients) solution. The patients then performed mouthwash with 10 mL of the solution for 2 minutes four times daily for 7 days. The treatment groups were comparable regarding age, smoking habits, and surgery. Laboratory variables measuring vitamin K-dependent coagulation factors were within therapeutic ranges (international normalized ratio 4.00 to 2.10). One of the clinics used a different method for these measurements and therefore the levels of coagulation factor X in plasma obtained for the three clinics were compared. No significant difference in the range at which surgery was performed was found between clinics. In the placebo group, 10 patients developed bleeding requiring treatment, while none of the patients treated with tranexamic acid solution had bleeding. This difference was statistically significant (P < .01). The treatment with mouthwash was well tolerated. It was concluded that patients on oral anticoagulants can undergo oral surgery within the therapeutic range without reducing the dosage of anticoagulants, provided that local antifibrinolytic treatment with tranexamic acid solution is instituted.