An anti-pattern is a commonly occurring solution that will always have negative consequences, when applied to a recurring problem. Code smells are considered to be symptoms of anti-patterns and occur at source code level. The lifespan of code smells in a software system can be determined by mining the software repository on which the system is stored. This provides insight into the behaviour of software developers with regard to resolving code smells and anti-patterns. This thesis presents a custom built application that computes the lifespans of certain types of code smells in a software repository. As a case study, this tool is applied on seven open source systems in order to answer research questions concerning the lifespan of code smells and the refactoring behaviour of developers. The results of this study reveal that engineers are aware of code smells, but not very concerned with their impact, given the low refactoring activity. Finally, several suggestions are given to further develop the application and to extend the work done in this thesis.