The pleasure of humans seems to be often found in crossing boundaries. However, crossing legal boundaries provides a compliance violation that can lead to serious consequences – especially in the highly regulated German healthcare system. Due to the large number of regulations, economic competition is strictly limited in the German healthcare sector creating a considerable conflict between economic pressure, entrepreneurial visions and legal requirements. The identification of clear boundaries, the exploration of creative leeway and the crossing of compliance-related prohibition zones is oftentimes difficult due to the considerable legal 'grey area' between black and white, which has not yet been fully clarified by case law. The use of these grey areas as well as the crossing of permissible boundaries takes place in various forms in reality. Cooperations in which a physician crosses the so-called sectoral boundary (Sektorengrenze) in his own person, for example as an affiliated or fee-based physician (Beleg- oder Honorararzt), and provides both inpatient (stationäre) and outpatient (ambulante) medical services, are of particular relevance. In this context, this article is intended to provide an overview of the most commonly used forms of combined outpatient and inpatient activities (intersectoral activities) by the same person and to highlight the associated compliance issues.