The consequences of political reunification for health and mortality have the unique character of a ‘natural experiment’. This is particularly true for the formerly divided German Baltic Sea region due to its cultural and geographic commonalities. This paper ascertains the changes and differences in premature mortality at ages 0–74 in urban and rural areas of the German states of Mecklenburg–Vorpommern (MV) and Schleswig–Holstein (SH) since reunification and the contribution made by ‘avoidable’ mortality. Using official cause-of-death data, the effectiveness of health care and health policies was measured based on the concept of avoidable mortality in terms of both amenable and preventable conditions. Methods of decomposition and standardisation were employed in order to erase the compositional effect from the mortality trend. As a result, mortality differences relate primarily to men and the rural areas of the German Baltic Sea region. Whereas the mortality levels in the urban areas of MV and SH have converged, the rural areas of MV still show higher levels of preventable and amenable mortality. The results show that the accessibility and quality of medical care in the thinly populated areas of MV and the effectiveness of inter-sectoral health policies through primary prevention, particularly with regard to men, have room for improvement.