The effects of intravenous latamoxef therapy at two doses of 3g and 6g daily for 7 days was assessed by various haemostatic parameters. With both doses, the prothrombin time, thrombin time and activated partial thromboplastin time remained within the normal range throughout the study. However, with the 6g day-1 dose there was a marked prolongation of the bleeding time associated with defective platelet aggregation to adenosine diphosphate and low dose collagen after 7 days therapy. With the 3g day-1 dose of latamoxef, there was no prolongation of the bleeding time and only minor changes in platelet aggregation responses.