In this paper, we present a reliability study of clock mesh distribution networks. We analyze the electromigration (EM) phenomena and demonstrate their occurrence in clock mesh networks (CMN). Due to shrinking feature sizes in more advanced technologies, EM is becoming a more prominent reliability issue. Process variation, power supply noise, and clock gating are some of the factors that can increase electromigration in the clock mesh. We identity the potential EM branches by investigating current flows under various conditions. Our study shows that a clock mesh optimized for certain configurations of clock sinks may experience electromigration due to asymmetrical bidirectional currents flowing in some grid segments.