His reign lasted only seven years--from B.C.181 to B.C.

174--and it is thus probable that he died before there was time for his second important conquest to have any further consequences.
Phraates had sufficient warning of his coming decease to make preparations with respect to a successor.

Though he had several sons, some of whom were (we must suppose) of sufficient age to have ascended the throne, he left his crown to his brother, Mithridates.

He felt, probably, that the State required the direction of a firm hand, that war might at any time break out with either Syria or Bactria; while, if the career of conquest on which he had made Parthia enter were to be pursued, he could trust his brother better than any of his sons to conduct aggressive expeditions with combined vigor and prudence.

We shall see, as the history proceeds, how Mithridates justified his choice.