With the advances in switching technologies, explicit rate (ER) switches are becoming popular since they perform better than explicit forward congestion indication (EFCI) switches. In the transitional period, the EFCI and ER switches may coexist in the same ATM network. Hence the efficiency of various ER schemes should be considered in the mixed EFCI-ER environment, not only in the homogeneous ER environment. In this paper we describe five ER control mechanisms and compare their performance in the mixed EFCI-ER environment. Simulation results show that these algorithms can interoperate with the EFCI switches. However, the behavior of these ER schemes in the mixed EFCI-ER environment is sometimes different from that in the homogeneous ER environment. These ER schemes are re-evaluated based on their interoperability with EFCI schemes.