In order to observe the effect of fiber diameter i.e., surface curvature on the adhesion and growth behavior of cells, the culture of fibroblast cells on PET fibers with different diameter (2.5, 7.0, 14.0 and 21.0㎚) has been performed. The morphology of cells grown on the PET fibers was observed by scanning electron microscope after 1, 3 and 6 days. On the fiber with 21.0㎚ diameter, it was observed that almost of cells were parallel along the fiber axis, whereas the cells were tended to wind onto the fiber with 7.0㎚ and 14.0. In the fiber with 2.5 ㎚, the cells were skewering or wrapping onto the fiber probably owing that the dimension of the fiber was smaller than that of cell body. Our results were compared with others where fibroblast cell were cultured growth on glass fibers with 108 and 250 ㎚. Even though the surface properties between PET and glass fibers were different, from these result it can be carefully suggested that the orientation degree of the cells increases, and decreases with decreasing fiber diameter, that is to say, the optimum orientation degree of the cell might be in the range of 21∼108 ㎛ diameter. It can be explained that cells tend to move onto plain surface rather than onto the concave side and the convex side. It can be also observed that almost of the cells were migrated, and oriented, consequently, grown along the fiber axis of the surfaces with the diameter of 2.5 7.0 14.0 and 21.0 ㎛, that is to say, fibers may be acted "contact guidance". It can be concluded that surface topology as curvature of fibers plays an important role for interaction behavior of the cells such as proliferation, migration, and locomotion.