Summary: We show that, when the field strength \(H\) of the NS-NS \(B\) field does not vanish, the coordinates \(x\) and momenta \(p\) of open string end points satisfy a set of mixed commutation relations among themselves. Identifying \(x\) and \(p\) with the coordinates and derivatives of the D-brane world volume, we find a new type of noncommutative space which is very different from those associated with a constant \(B\) field background.