The aim of guidelines is to increase the quality of care in clinical practice. Any influence or financial support by the pharmaceutical industry must be excluded. In urology only two S3 guidelines have been published in German and all others are more or less recommendations (S1). The example of the second opinion project on testicular germ cell tumors shows that a reduction of recurrence, morbidity and mortality can be achieved by the consistent application of guidelines. Oncological guidelines are often focused on the unidirectional parameter overall survival but do not include other important aspects, such as long-term morbidity or quality of life.