Many network monitoring tools do not provide sufficiently in-depth and useful reports on network usage, particularly in the domain of application services data. Application services form an integral part of organizational networks. The optimization of the performance of these networks is only possible if the networks are effectively monitored. Techniques that identify patterns of network usage can assist in the successful monitoring of network performance. The focus of this paper is on the development of a visual data mining prototype, called NetPatterns, which facilitates the effective visualization of network performance data.