First onset of a generalized tonic-clonic seizure is a frequent reason for hospital admissions. This article aims to provide a brief overview of the epidemiology, etiology, investigation and treatment of a first generalized tonic-clonic seizure.The review is based on a discretionary sample of English-language articles found through a search in PubMed, and the authors' own clinical experience.A first generalized tonic-clonic seizure is traditionally divided into either a provoked or an unprovoked seizure. Provoked seizures occur in close temporal relationship to a systemic disorder or to a brain insult, for example a stroke or a head trauma. Unprovoked seizures occur in the absence of such factors. The incidence of provoked and unprovoked seizures is 35/100.000 person years and 50/100,000 person years, respectively. The occurrence is influenced by genetic and lifestyle factors. The hospital assessment includes a thorough case history, a somatic and neurological examination, ECG, standard EEG, and cerebral MRI. An immediate cerebral CT is often carried out. In case of provoked seizures, both treatment and estimation of the recurrence risk depends on the underlying cause. Antiepileptic drug treatment initiated after a first unprovoked seizure may reduce the risk of seizure recurrence. However, no long term risk reduction has been shown compared to delaying treatment until after a second seizure.Patients who experience a first generalized tonic-clonic seizure are a heterogenous group, and a thorough diagnostic assessment is necessary in order to provide tailored treatment and a reliable prognosis.