This research, based on a study of King George III's medical records and of contemporary diaries of his courtiers and equerries, further confirms the considerable doubt on the claim of Richard Hunter and Ida Macalpine that the King suffered from recurrent attacks of acute porphyria.The present study examines the above records from a psychiatric viewpoint, together with some additional reports, to re-assess the nature of the King's maladies. It concludes that he suffered from recurrent mania (four episodes), with chronic mania and possibly a degree of fatuity during the last decade of his life.This is in agreement with previous reports that he suffered from manic-depressive psychosis.