Informing patients about risks and benefits of alternative treatment options and choosing between them is becoming a bigger challenge as knowledge about the relationship between the individual's genetic profile and the efficacy and safety of available medications accumulates. Putting personalized medicine into practice requires new modes of information sharing and decision making by patient and physician. This is illustrated by a case study on treatment choices of breast cancer patients following genotyping for CYP2D6, recently published in Genome Medicine.See research article: http://genomemedicine.com/content/3/10/64.