“Life is lumpy. A lump in the oatmeal, a lump in the throat, and a lump in the breast are not the same kind of lump. One needs to learn the difference,” says author Robert Fulghum. So too with clinical trials. A forgotten vital signs value, a missing primary endpoint, and an unplanned interim analysis are not the same kind of protocol deviation. We need to know the difference, and the repercussions. In this session we discuss different types of protocol deviations and their implications, statistical and otherwise.