The randomized controlled trial (RCT) is the cornerstone of evidence‐based medicine and has been a key factor in the rapid advances in medicine over the last 50 years. The key to a properly conducted RCT is that the sequence generation is properly randomized and that the investigator is not aware what the next sequence will be before the patient is entered into the trial (concealment of allocation). This will ensure that the experimental groups are well balanced for any factors that may influence outcomes of the trial. Ideally participants, healthcare staff, and researchers should be blinded to the intervention being received and there should be minimal loss of follow‐up. If this is achieved then biases will be minimized. There are many types of RCTs including parallel group, factorial, cross‐over, and cluster randomized trial. The choice of design depends on the setting and the question being evaluated.