Today, the combined use of Oriental herbal medicines and Western biomedical medicines has been a prevalent yet controversial practice. Case reports and healthy volunteer trials have had conflicting results on the effect Panax ginseng has on warfarin's pharmacologic action, some reporting a reductive and others a potentiating influence. This study investigated the interaction between warfarin and P. ginseng by observing the prothrombin time (PT) and the international normalized ratio (INR) in ischemic stroke patients who did not have a history of taking warfarin. Randomized, open-label, controlled study. Twenty-five (25) patients newly diagnosed with ischemic stroke by brain computed tomography or magnetic resonance imaging in the Korean Medical Hospital, Kyung Hee University (Seoul, Republic of Korea). Ischemic stroke patients were randomized into 2 groups: the ginseng group (n = 12), given both P. ginseng and warfarin, and the control group (n = 13), given only warfarin, both for 2 weeks. The warfarin dose was restricted to 2 mg in the first week and 5 mg in the second week. The peak values and the international normalized ratio (INR) and prothrombin time (PT) areas under the curve (AUC) in both groups significantly increased compared to those at baseline. However, there was no statistically significant difference in peak values and INR and PT AUC between groups in both the first and second weeks. This study suggests that coadministration of P. ginseng and warfarin in ischemic stroke patients does not influence the pharmacologic action of warfarin.