Evidence for surgical practice should be based on high-quality data, some of which would originate from well-designed and executed randomized controlled trials (RCTs). Subgroup analyses are often reported within RCT results and they aim to identify either consistencies or large differences in different categories (or subgroups) of patients. However, subgroup analyses can sometimes be misleading. The purpose of this article is to outline the criteria for rigorous subgroup analyses in methodologically sound RCTs. A clinical scenario based upon a recent RCT in general surgery will support these criteria throughout the text.