The hydration process of fresh concretes with different proportions was studied using electrical resistivity measurement. The minimum point (P) and the transition point (P) were identified on the electrical resistivity development curves. The time t at which P occurred, represented the time when the curve dropped to a minimum and before increasing as a result of the onset of hydration. The time t at which P occurred, marked the time when the kinetics of hydration transition changed from the setting to the hardening stage. To evaluate the significance of t and t in terms of the setting process, they were compared to the initial setting time (t) and final setting time (t) measured with the traditional penetration resistance method. The quantitative relationships between the setting time of concrete and the electrical resistivity critical points were developed. The equations can be used to estimate the setting times of concrete as an alternative method. © 2007 ASCE.