Software maintenance is a resource-intensive, costly task, performed on complex products. It is especially demanding in large-scale telecommunication systems. The improvement of software maintenance process is of particular interest for software development organizations. The problem the thesis addresses is the analysis of the software maintenance process that will lead to process improvement. The information gathered during modeling, analysis and evaluation of an existing process can point to process deficiencies enabling thus process improvement. The thesis presents the method for the analysis and improvement of software maintenance processes. The method enables objective description and evaluation of an existing maintenance process with the goal of identifying process changes that will lead to process improvement. The method comprises the following steps: maintenance process modeling, definition of metrics for process analysis and evaluation, data collection and processing, data analysis based on statistical tests of hypothesis, process evaluation from the customer's perspective, identification of process changes that will lead to process improvement, and introduction of process changes. The method uses existing techniques for process modeling and analysis taking into consideration technical and organizational process characteristics. Specification and Description Language (SDL) has been employed for process modeling. Hypothesis tests have been applied for the analysis of process data. Special model for process evaluation from the customer's perspective has been defined. Process changes that will lead to process improvement have been investigated applying process simulation. The method has been applied for modeling, analysis and evaluation of the maintenance process performed in a large telecommunications company. The method enables process understanding, monitoring, gradual extension of an existing metrics program, and iterative process improvement. The method has a cyclic approach and should therefore be performed in parallel with the real maintenance process.