The sealing ability of five commonly used endodontic sealer/cements (Procosol, Diaket, Tubliseal, N2, and Nogenol), was studied by an electrochemical technique. Extracted teeth were prepared biomechanically and the root canals were sealed with one of the sealer/cements. Ten teeth were used for each material without an accompanying solid core. Microleakage was determined over a period of 30 days. The degree of leakage for the materials tested decreased in the following order: Diaket, Tubliseal, Nogenol, ProcoSol, N2. On the basis of this study and previously reported histopathologic studies of tissue compatibility, it appears that ProcoSol is the material of choice as an endodontic sealer/cement.