PER CURIAM
On father's petition for reconsideration, we are persuaded that the fact that both parents seek to modify the original decree granting joint custody of their children to mother and father, each of whom now seek sole custody, constitutes a substantial change of circumstances requiring a modification of the child custody provisions of the original decree. See Heinel and Kessel, 55 Or. App. 275, 637 P.2d 1313 (1981). Because the trial court found no substantial change of circumstances, it did not consider in what respect the custody provisions of the decree should be modified. That court is in the best position to make the initial determination in change of custody cases; accordingly, we remand the case to the trial court to decide whether mother or father should be given custody of the twin boys of the parties. Father does not seek custody of the parties' daughter.
Petition granted; former opinion modified and case remanded.