Pediatric drug development using some form of extrapolation (esp., a drug that has been approved for adults) range along a continuum of clinical programs to support the drug’s efficacy in children. For example, a single adequate well controlled efficacy and safety trial and PK study, a single uncontrolled efficacy and safety trial and PK study, a single exposure-response trial, a PK and a safety study, a PK/PD study and an uncontrolled efficacy and safety trial, a PK/PD and a safety study have been used. This talk focuses on some issues encountered in programs requiring a single adequate and well controlled efficacy and safety study. In particular, it is unclear what is the real hypothesis that need to be tested – whether it is a confirmation of efficacy and/or confirmation of similarity of response. It is also unclear what is the interpretation of type I error in the setting of extrapolation or if it even make sense. Moreover, is an adjustment for multiplicity in testing multiple endpoints even useful or an unnecessary burden?