Ultrafine particles represent the smallest size fractions of particles with sizes from one to about 100 nanometers in aerodynamic diameter . Thus, their specific health effects are related to their physical capacity to reach diverse organ systems. The aims of this project were to systematically review the scientific literature on the health effects of ultrafine particles, to evaluate the quality of the selected studies and to assess the transferability of the results to the situation in Germany. The  search strategy yielded 85 references of original articles. As a result, the evidence on health effects related to the exposure with ultrafine particles remains inconclusive or insufficient for most of the studied health outcomes.