Post-traumatic vomiting was clinically analyzed. One hundred and forty seven patients with head injury came to our hospital consecutively from April 1991 to August 1991. Of 147 patients, 26 exhibited vomiting post-traumatically. The incidence of loss of consciousness, that of fractures on plain X-ray films, and that of traumatic intracranial lesions demonstrated on CT were compared between two patient groups, i.e., a group of patients with post-traumatic vomiting and another one without it. None of them were revealed to be significantly different between the two groups, respectively. It was concluded from the results that the existence of post-traumatic vomiting implied neither severe traumatic impact nor serious intracranial damage. The plausible mechanisms of post-traumatic vomiting are discussed, taking account of the statistical data on the patients' age, sites of impact, and past histories.