An active contour model, Snake, was developed as a useful segmenting and tracking tool for rigid or non-rigid (i.e, deformable) objects by Kass in 1987. Snake is designed on the basis of Snake energies. Segmenting and tracking can be executed successfully by the process of energy minimization. The ability to contract is an important process for segmenting objects from images, but the contraction forces of Kass' Snake are dependent on the object's form. In this research, new contraction energy, independent of the object's form, is proposed for the better segmentation of objects. Kass' Snake can be applied to the case of small changes between images because its solutions can be achieved on the basis of variational approach. If a somewhat fast moving object exists in successive images, Kass' Snake will not operate well because the moving object may have large differences in its position or form, between successive images. Snake's nodes may fall into the local minima in their motion to the new positions of the target object in next image. When the motion is too large to apply image flow energy to tracking, a jump mode is proposed for solving the problem. The vector used to make Snake's nodes jump to the new location can be obtained by processing the image flow. The effectiveness of the proposed Snake is confirmed by some simulations. (C) 2000 Published by Elsevier Science Ltd.