We report the pharmacological treatment of a case of alternating hemiplegia of childhood (AHC) in a 14-year-old female with an established diagnosis. Although the patient's symptoms are consistent with those of the condition, she did not respond to treatment with haloperidol, flunarizine, or propranolol. Treatment with aripiprazole resulted in a reduction in the frequency, duration, and severity of episodes of alternating hemiplegia, along with other therapeutic benefits. After treatment with aripiprazole was started, the patient was inadvertently given an inactive drug, resulting in a worsening of her hemiplegic episodes, which improved again on rechallenge. A comparison of the pharmacological actions of successful and unsuccessful treatments for AHC is made. Modulation of both dopamine and histamine systems together appears to be important in the treatment of AHC and further investigation of such pharmacotherapies is suggested.