Transparency is essential for the efficient transfer of scientific knowledge from research into practice but is often impaired by non-publication of whole studies or by inappropriate publication of trial results. Prospective trial registration has the potential to increase transparency in scientific research because it allows the evaluation of trial methodology and the appraisal of potential publication bias. Trial registration is a scientific, ethical and moral obligation which needs self-commitment of researchers and sponsors to prospective trial registration. The urological trial register of the German Society of Urology is now affiliated with the German Register of Clinical Studies, a national primary register, which enables easy registration in the register network of the WHO.