Security engineering in the software lifecycle aims at protecting information and systems to guarantee confidentiality, integrity, and availability. As security engineering matures and the number of research papers grows, there is an increasing need for papers that summarize results and provide an overview of the area. A systematic mapping study "maps" a research area by classifying papers to identify which topics are well-studied and which need additional study. Therefore, systematic mapping studies are becoming increasingly important in security engineering. This chapter provides methodological support for systematic mapping studies in security engineering based on examples from published security engineering papers. Because security engineering is similar to software engineering in that it bridges research and practice, researchers can use the same basic systematic mapping process, as follows: (1) study planning, (2) searching for studies, (3) study selection, (4) study quality assessment, (5) data extraction, (6) data classification, (7) data analysis, and (8) reporting of results. We use published mapping studies to describe the tailoring of this process for security engineering. In addition to guidance on how to perform systematic mapping studies in security engineering, this chapter should increase awareness in the security engineering community of the need for additional mapping studies.