In this article I intend to reveal the old, orally-transmitted heroic tale that lies behind the Jephthah story in the Book of Judges, which is obscured by massive Deuteronomistic and post-Deuteronomistic additions and redactions. The old story deals with a conflict on the settlement boundary between Israelites and Ammonites in Transjordan, around the towns of Gilead and Mizpah. It probably reflects realities before, or in the early days of the Northern kingdom.