Together with large biobanks of human samples, medical registries with aggregated data from many clinical centers are vital parts of an infrastructure for maintaining high standards of quality with regard to medical diagnosis and treatment. The rapid development in personalized medicine and pharmaco-genomics only underscores the future need for these infrastructures. However, registries and biobanks have been criticized as constituting great risks to individual privacy. In this article, I suggest that quality with regard to diagnosis and treatment is an inherent, morally normative requirement of health care, and argue that quality concerns in this sense may be balanced with privacy concerns.