The electrostatic discharge (ESD) problem has become a challenging reliability issue in nanometer-circuit design. High voltages that resulted from ESD might cause high current densities in a small device and burn it out, so on-chip protection circuits for IC pads are required. To reduce the design cost, the protection circuit should be added only for the IC pads with an ESD current path, which causes the ESD current path analysis problem. In this paper, we first introduce the analysis problem for ESD protection in circuit design. We then model the circuit as a constraint graph, decompose the ESD connected components (ECCs) linked with the pads, and apply breadth-first search (BFS) to identify the ECCs in each constraint graph and, thus, the current paths. Experimental results show that our algorithm can very efficiently and economically detect all ESD paths. For example, our algorithm can detect all ESD paths in a circuit with more than 1.3 million vertices in 1.39 s and consume only 44-MB memory on a 3.0-GHz Intel Pentium 4 PC. To the best of our knowledge, our algorithm is the firstpointtool available to the public for the ESD analysis.