Atomic steps were rearranged during step-flow growth of Si epitaxial layers on 0.6- and 1.5-mu m-wide Si(111) mesas oriented in the [11 (2) over bar] direction during molecular beam epitaxy. Ge islands were then grown on the mesa tops to form well-positioned arrays of self-assembling nanodots. On the 0.6-mu m-wide mesas, the Si growth produced arrays of arrowheads composed of [(1) over bar (1) over bar 2]-type bunched steps. Ge islands preferentially grow at the vertices of arrowhead-like steps, aligning along the center of a mesa. On 1.5-mu m-wide mesas, on the other hand, the resulting steps have a zigzag-shaped pattern and Ge islands also preferentially grow at the vertices of zigzag steps. These results demonstrate that by using atomic steps with artificially designed arrangement, it is possible to position and align the Ge islands on Si(111) mesas.