This article reviews the evidence regarding the use of phenytoin in adult and paediatric patients experiencing seizures in the ED in Australasia, including relevant pharmacokinetics, dosage, therapeutic drug monitoring and methods of administration. It summarizes current evidence regarding the use of phenytoin in a number of seizure types commonly seen in ED. A search of Medline, Embase and Cochrane was performed using appropriate keyword and MeSH headings. A loading dose of phenytoin should be given to phenytoin naïve patients for the emergency treatment of seizures; parenteral administration results in therapeutic concentration sooner than oral administration but is associated with more frequent and significant adverse effects. Diluting phenytoin is safe but there is limited evidence regarding adverse effects of diluted phenytoin; a filter is probably not needed. Free phenytoin concentrations correlate best with antiseizure efficacy. Phenytoin is used in the treatment of status epilepticus although evidence here is limited; it may also be given to prevent early post-traumatic seizures. It should not be given to treat or prevent eclamptic or alcohol-related seizures. There is insufficient evidence regarding its use in preventing febrile convulsions, treating or preventing seizures due to space occupying lesions or intracerebral haemorrhage and thrombosis. In conclusion, phenytoin is appropriate for treatment of some seizures seen in the ED; it is associated with significant adverse effects; trials are ongoing regarding the use of other anticonvulsants in the treatment of status epilepticus.