While many theoretical approaches to security engineering exist, they are often limited to systems of a certain complexity, and require security expertise that is not widely available. Additionally, in the practice of information system development security is but one of many concerns that needs to be addressed, and security concerns are often dealt with in an ad hoc manner. Security patterns promise to fill this gap. Patterns enable an efficient transfer of experience and skills. However, representing and selecting security patterns remains largely an empirical task. This becomes the more of a challenge as the number of security patterns documented in the literature grows, and as the patterns proposed by different authors often overlap in scope. Our contribution is to use a more explicit representation of the forces addressed by a pattern in the description of security patterns, which is based on non-functional requirements analysis. This representation helps us decide which patterns to apply in a given design context, and anticipate the effect of using several patterns in combination. Specifically this chapter describes an approach for selecting security patterns, and exploring the impact of applying these patterns individually, and in concert with other patterns.