He succeeded his father as king in 272 BC, and continued the war which his father had begun with Antigonus II Gonatas, whom he succeeded in driving from the kingdom of Macedon. He was, however, dispossessed of both Macedon and Epirus by Demetrius II of Macedon, the son of Antigonus; upon which he took refuge amongst the Acarnanians. By their assistance and that of his own subjects, who entertained a great attachment for him, he recovered Epirus. It appears that he was in alliance with the Aetolians. He married his sister Olympias, by whom he had two sons, Pyrrhus and Ptolemaeus, and a daughter, Phthia. On the death of Alexander, around 242 BC, Olympias assumed the regency on behalf of her sons, and married Phthia to Demetrius. There are extant silver and copper coins of this king. The former bear a youthful head covered with the skin of an elephant's head. The reverse represents Pallas holding a spear in one hand and a shield in the other, and before her stands an eagle on a thunderbolt.