Scientific attention for medication adherence among people with chronic diseases has grown exponentially during the last decades. Despite the fact that the prevalence of DM is higher in non-White ethnic minorities only few studies on adherence to OHA in these populations were published. In chapter 1 (section 2), we presented the results of our systematic literature review on adherence to OHA in non-White ethnic minorities. Demographic, disease-related, treatment-related, socioeconomic and cultural factors were associated with adherence to OHA in the non-White ethnic minorities under study. However, because the included studies suffered from several methodological difficulties we also proposed methodological improvements for future research. The systematic literature review drew our attention to the multitude of factors, some of which may be culturally shaped, influencing adherence to OHA. As such it lay the foundation for our qualitative research study in which we explored perspectives of T2DM-patients of Turkish descent. Furthermore, the, often limited, insights and methodological shortcomings of the included studies strengthened the argumentation for our research design in which a detailed exploration, using qualitative methods, would precede a quantitative assessment of factors influencing OHA. To explore factors influencing adherence to OHA among T2DM-patients of Turkish descent we first conducted a qualitative study, using in-depth interviews (chapter 3). A theoretical sampling procedure was used, meaning analysis results of earlier conducted interviews led to adjusted or new inclusion criteria for patients to be interviewed in the course of the study. This process stopped when theoretical saturation was reached. This cycle of data collection, data analysis and selection of new cases provided us with a broad overview of factors potentially influencing adherence to OHA and a detailed exploration of how influencing factors are interconnected. Furthermore, this theoretical sampling procedure guaranteed the ...