The results of a well-designed and executed clinical trial should be evident from a few summary statistics — but stopping at those summaries in a manuscript is rare. It is reasonable to want to see if more can be learned from a long, expensive eﬀort. The temptation to overinterpret secondary analyses can be irresistible. Although exploring data and analyzing diﬀerent endpoints do sometimes lead to new insights, far too often they lead to implausible hypotheses and faulty conclusions. In this chapter we discuss problems with some common types of analyses that have been used to try to draw treatment conclusions beyond those supported by the study design. In Chapter 9 we discuss methods for exploratory data analysis.