On a local level, his regular dominance of the Nordic and Norwegian Chess Championships during the 1980s amply demonstrated that there were few players who could resist his enterprising and inventive style.

In international competition, he finished second at the 1986 World Junior Championship behind Walter Arencibia and ahead of Evgeny Bareev, Viswanathan Anand and Jeroen Piket.

In the late 1980s, Agdestein combined top-flight chess with a full-time football career, representing his country at both.

[6] As a player of the white pieces, he shows a preference for the queen pawn openings, while with Black, favours the Ruy Lopez, Dutch Defence and Semi-Open Games.

He was born in Oslo as a son of civil engineer Reidar Frank Agdestein (1927–2002) and secretary Unni Jørgensen (1934–).