Objective: This study was undertaken to determine the relative shear bond strengths and microleakage of 4 bonding agents to dentin and amalgam and to investigate the bonding to dentin through confocal laser scanning microscopy. Method and materials: Sixty noncarious molars were restored with 1 of 4 different systems, and the shear bond strengths were determined. For the microleakage study, Class V amalgam restorations were placed in 60 noncarious teeth. The specimens were thermocycled, the teeth were sectioned, and dye penetration was assessed. For confocal examinations, the first component of the bonding adhesives was labeled with rhodamine B. Each of the adhesives was applied to 3 dentin specimens, which were examined under a confocal laser scanning microscope. Results: Of the 4 restorative systems tested, AmalgamBond Plus + HPA and Prime & Bond 2.1/base-catalyst showed significantly higher shear bond strengths. Prime & Bond 2.1/base-catalyst had the lowest microleakage value, which was significantly lower than that of AmalgamBond Plus + HPA and AmalgamBond Plus. AmalgamBond Plus + HPA had the highest variation in both the bond strength and microleakage values. Confocal laser scanning microscopy revealed tag formation, penetration of the bonding agents deep into the tubules, and hybrid layer formation for all 4 bonding systems. Conclusion: The 2 best systems, Prime & Bond 2.1/base-catalyst and, to a lesser extent, AmalgamBond Plus + HPA, utilized a supplemental bonding agent.