A new algorithm for segmenting and tracking deformable (shape-changing) linear (thin and long with negligible diameter) objects in video images is presented. The core of algorithm is to detect the two boundary curves of a deformable linear object within adaptive tracking windows. The boundaries are found by analyzing the gray value gradients within the tracking windows. The algorithm allows moderate changes in the image brightness by introducing tolerance parameters to the algorithm. It also provides a robust tracking of the shape- and width-changing object by using a fuzzy estimation of the object's membership function at the tracked points. The result resulting describes the shape of the object and is used to define features for shape change detection.