Grounded theory methodology is one of the most widely used approaches to collect and analyze data within qualitative research. It can be characterized as a framework for study design, data collection, and analysis, which aims at the development of middle-range theories. The final result of such a study is called a “grounded theory,” and it consists of categories that are related to each other. Health and risk message design researchers working with grounded theory methodology are explicitly invited to use any kind of data they consider suitable for a particular project. Grounded theory methodology studies were originally based on intense fieldwork data, but in the meantime, interviews have become the most widely used type of data. In addition, there is a growing interest in using visual data such as pictures or film. Grounded theory methodology originated from sociology, but has since been applied in many different disciplines. This widened application went along with modifications, new developments, and innovations, and led to several current variants of grounded theory methodology. Basic features of grounded theory methodology include theoretical sampling, specific coding procedures with a comparative approach to analysis, and memo writing. The strategy of theoretical sampling requires that theoretical insights gained from the analysis of initially collected data guide subsequent data collection. Hence, during the research process data collection and analysis alternate and interact. For data analysis, different ways of coding enable the researcher to develop increasingly abstract conceptual ideas and reflections, first embodied in codes, later in categories. This analytical process allows for a step-by-step development of categories that are grounded in data. Category development entails comparisons at all stages, for example, of different cases during sampling, of different data pieces, and of different codes and categories during analysis. As a result, grounded theory methodology is also known as the constant comparative method. Throughout the research process the researcher writes memos and keeps track of the development of conceptual ideas, methodological reflections, and practical to-dos. Today, many researchers use software specifically developed to assist the process of qualitative data analysis.