Objectives: This study evaluated the single-dose toxicity of Saeng Maek San (SMS) in rats. Methods: All experiments were conducted at Biotoxtech (Chungwon, Korea), an institute authorized to perform non-clinical studies under the regulations of Good Laboratory Practice (GLP). A single-dose intravenous toxicity study was carried out on 40 6-week-old Sprague-Daley rats. The animals were randomly divided into the following four groups of ten animals each: Group 1 (G1) was the control group, with each animal receiving an intravenous injection of 1.0 mL of saline, and Groups 2, 3 and 4 (G2, G3 and G4) were the experimental groups, with the animals in the groups receiving an injection of 0.1, 0.5 and 1.0 mL of SMS, respectively. Mortality, clinical signs, body-weight changes and gross pathological findings were observed for 14 days following a single administration of SMS or saline. Organ weights, clinical chemistry and hematology were analyzed at 14 days. This study was conducted with the approval of the Institutional Animal Ethics Committee. Results: No deaths occurred in any of the four groups, indicating that the lethal dose of SMS in rats is greater than 1.0 mL/animal. Some changes in weights of male rats between the control group and the experimental groups were observed, but no significant changes in the weights of female rats were noted. To identify abnormalities in organs and tissues, we stained representative sections of each specified organ with hematoxylin and eosin for examination with a light microscope. No significant abnormalities were observed in any of the organs or tissues. Conclusion: The results suggest that intravenous injection of SMS is a safe method of treatment.