As a new technology of biometrics, gait recognition has attracted a great deal of interest in computer vision community due to its advantage of unobtrusive recognition at a distance. In this paper, a review of this topic is presented in terms of approaches, databases and challenges. First, a comprehensive survey of recent developments on gait recognition approaches is reported, where relevant techniques are categorized into three classes for discussions. Then, more than 10 publically available datasets are analysed and compared in detail. In addition, challenges that constrain practical application of gait recognition systems are discussed. Finally, future trends are given to guide further research in this field. (6 pages)