Purpose: to evaluate and compare microleakage of single cone and lateral condensation obturating techniques of straight and single curved canals, using electrochemical method over a three-month period. And to assess the adaptation between the filling and dentin of the root canal wall using SEM. Materials and methods: Forty freshly extracted maxillary first molars will be used in the study. The teeth were decapitated at the cemento-enamel junction and the palatal and the mesio-buccal roots were separated. The root canals were shaped using the ProTaper Universal Nickel-Titanium rotary system, then obturated with either single cone or lateral condensation technique. All samples were tested using electrochemical model for leakage evaluation over 12 weeks period, then sectioned and scanned with SEM. Results: Single cone showed the high mean electrical resistance over the test period than the lateral condensation technique, with insignificant difference between them. Conclusions: Varying degrees of leakage were evident that increased over time. The magnitude of leakage was small and would tend to support the clinical use of single cone filling technique especially in curved canals.