Synchronization of the applause with leaders is investigated. The cases of the presence or absence of the effect of the applause transmission time delay on the part of the spectators are considered rcspectively. Sufficient conditions for the applause synchronization are presented for each case. The obtained theoretical results not only manifest the observation that rhythmic applauses are more frequently heard in a theater with high attendance rate, but also show a surprising conclusion that one leader is enough to make all spectators clap with the same frequency in a very large theater. Furthermore, numerical examples are provided to illustrate the validity of the theoretical results.