Microleakage can occur at the abutment-implant (A-I) interface in osseointegrated implants and may cause malodor and inflammation of peri-implant tissues. The degree of microleakage at the A-I interface of 5 implant systems was comparatively assessed at varying closing torques. Using colored tracing probes driven by a 2-atm pressure system, the interface microleakage of Brånemark, Sulzer Calcitek, 3i, ITI, and Steri-Oss implants was determined spectrophotometrically. Microleakage through the A-I interface occurred in all systems, with variability between systems, samples, and closing torques. As closing torque increased from 10 Ncm to 20 Ncm to manufacturers' recommended closing torques, microleakage decreased significantly (P .005) for all systems. Analysis of variance showed significant interaction between closing torques and the time course of microleakage, and between systems and the time course of microleakage (P .001). The results indicate that fluids and small molecules are capable of passing through the interface of all the A-I assemblies studied. Presumably in an in situ situation, fluids containing bacterial byproducts and nutrients required for bacterial growth may pass through the interface gap, contributing in part to clinically observed malodor and peri-implantitis. Keywords: closing torque, implant, microleakage, preload, screw loosening