We studied the acute oral toxicity of black ginseng (BG) produced by heat process in rats. Single acute BG extract doses of 0, 5, 10, and 15 g/kg dissolved in saline were administered by oral gavage and the animals were kept under observation for 14 days. The single administration of BG extract up to 15 g/kg did not produce mortality, behavioral change or abnormal clinical signs in the rats. These results indicated that the oral $LD_{50}$ of the BG extract in the rats is higher than 15 g/kg. Compared to the control group, no treatment-related biologically significant effects of BG extract were noted in the measurements of the body weight or food intake. At the end of the period, the biochemical parameters and hematological parameters were analyzed in the plasma and blood. A histopathological examination of the liver and kidney was also conducted. Only the blood nitrogen urea and potassium levels in the biochemical indices showed significant differences at 10 and 15 g/kg doses of BG extract compared to the control group. These changes were not considered to be due to the toxicity. None of the other clinical chemistry parameters were affected. Therefore, these results indicate that the BG by heat processing is virtually nontoxic.