As organizations accumulate data over time, the problem of tracking how patterns evolve becomes important. In this paper, we present an algorithm to track the evolution of cluster models in a stream of data. Our algorithm is based on the application of bounds derived using Cherno 's inequality and makes use of a clustering algorithm that was previously developed by us, namely Fractal Clustering, which uses self-similarity as the property to group points together. Experiments show that our tracking algorithm is e cient and e ective in nding changes on the patterns.