The bioavailability of tranexamic acid after the administration of a single intramuscular dose was estimated in three healthy male volunteers. 500 mg tranexamic acid were given intramuscularly and intravenously, as a bolus injection, to each subject on separate occasions. Following intramuscular administration, the peak plasma concentrations were attained after approximately one hour and the apparent elimination half-life was about two hours. The absolute bioavailability was 105.2 +/- 10.7% (mean +/- SD). At the dose given, the bioavailability of tranexamic acid after intramuscular administration is fast and complete.