Patients are unique, and improvements in medicine and laboratory technology are showing that drug exposure and its effects can be very different in an individual patient despite receiving the same dose.  Therapeutic drug monitoring is becoming a more recognized and utilized tool to improve patient-specific drug efficacy and reduce toxicity, especially in the areas of oncology and HIV/AIDS. Dr. Rosa Yeh, Director of the Pharmacokinetics Laboratory at the Seattle Cancer Care Alliance reviews recent laboratory and clinical trial evidence regarding drugs in oncology and HIV/AIDS and the benefit of therapeutic drug monitoring. From the Series:Laboratory Medicine Grand Rounds