Subgroup analyses in randomized clinical trials: value and limitations. Review #3 on important aspects of randomized clinical trials in cardiovascular pharmacotherapy. Issue 3 (28th June 2021) - Drexel, Heinz; Pocock, Stuart J; Lewis, Basil S; Saely, Christoph H; Kaski, Juan Carlos; Rosano, Giuseppe M C; Tautermann, Gerda; Huber, Kurt; Dopheide, Joern F; Mader, Arthur; Niessner, Alexander; Savarese, Gianluigi; et al.