The in vivo single-dose acute toxicity of Lactobacillus plantarum AF1, a lactic acid bacterium isolated from kimchi, in ICR male and female mice was investigated. The test article was intraperitoneally or orally administered once to both sexes of mice. The motalites, clinical findings, autopsy findings, and body weight changes were monitored daily for 14 days. In the oral acute toxicity test, the male and female mice were gavaged with four doses (5.0, 2.5, 1.25 and 0.625 g/kg) of Lb. plantarum AF1. The oral LD50 of the Lb. plantarum AF1 was considered higher than 5.0 g/kg. In the intraperitoneal acute toxicity test, mice were injected intraperitoneally with dosages of 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.3 and 2.5 g/kg. The intraperitoneal 50% lethal dose (LD50) of the Lb. plantarum AF1 was >2.5 g/kg in the male and female mice. No significant changes in the general conditions, body weights, clinical signs, and gross lesions were observed in both sexes of mice to which Lb. plantarum AF1 was administered intraperitoneally or orally. The results suggest that the no-adverse-effect level of Lb. plantarum AF1 is estimated to be more than 5.0 g/kg in the oral route and 2.5 g/kg in the intraperitoneal route.