A 74-year-old man with a remote history of Sydenham's chorea but no personal or family history of mood disorder had simultaneous onset of severe, generalized chorea and a mild manic syndrome in clear consciousness. Both chorea and hypomania improved after treatment with sodium valproate and clonazepam. Agitated delirium or mood lability have been described in Sydenham's, but this case is the first report of criteria-based secondary mania with probable Sydenham's chorea, as well as the longest reported remission between symptomatic Sydenham's episodes. The parallel course of this patient's hypomania and chorea supports current pathophysiologic theories of idiopathic mania.