Toxic hepatitis has recently been discovered to be a major cause of acute hepatitis. We studied the clinical features and prognosis of patients diagnosed with toxic hepatitis at a single institution. A retrospective analysis was performed using medical records of 159 cases of toxic hepatitis that were diagnosed from March 2003 to March 2008. Patients were selected based on a RUCAM score of 4 or above. The incidence was higher in women (n=97) than in men (n=62). The age (mean+/-SD) of the patients was 51+/-15 years . The major causes of the disease included the use of Korean traditional therapeutic preparations (34.0%), herbal medicines (41.5%), and drugs prescribed by a physician (23.9%). At the time of admission, jaundice was the most common symptom (41.5%), and the results of a liver serum battery were as follows: aspartate aminotransferase, 729.4+/-877.0 IU/L; alanine aminotransferase, 857.1+/-683.0 IU/L; total bilirubin, 6.4+/-6.5 mg/dL; and alkaline phosphatase, 209.8+/-130.0 IU/L. The hospitalization period was 10.0+/-9.5 days, and the duration of recovery from liver injury was 31.0+/-29.5 days. The factors associated with the hospitalization period included the presence of anorexia and the serum levels of albumin and bilirubin at the time of admission (P<0.05). A high serum bilirubin level and a history of alcohol ingestion were associated with a delayed recovery (Plt;0.05). The sex, age, BMI, and duration of medication were not significantly related to the hospitalization and recovery periods. The main cause of acute toxic hepatitis in the current study was the use of herbal medicines. The severity of liver injury at the time of admission was a major factor significantly associated with the hospitalization and recovery periods.