Purpose: To evaluate the effect of saliva contamination on shear bond strength, microleakage, and microstructure of the adhesive interface in two different adhesive systems by using scanning electron microscopy (SEM) and confocal laser microscopy (CLSM). Materials and methods: Randomly, 228 third molars were allocated to six groups for an etch-and-rinse adhesive One-Step Plus (Bisco Inc.) and a self-etch adhesive G Bond (GC Corp.): Group 1 - manufacturer's instructions were followed; Group 2 - involved contamination and drying before adhesive application; Group 3 - involved contamination, washing, and blot drying before adhesive application; Group 4 - involved contamination, etching, washing, and blot drying before adhesive application; Group 5 - involved contamination and drying after adhesive application, followed by adhesive reapplication; Group 6 - involved contamination and washing after adhesive application, followed by adhesive reapplication. Shear bond strength was tested after specimens were stored in distilled water at 37 degrees C for 24h. Specimens were evaluated under a stereomicroscope for microleakage. Dentin-resin interfaces were evaluated by SEM and CLSM. Results: Group 2 for One-Step Plus and Group 3 for G Bond showed significantly lower bond strengths than control groups. Microleakage values were significantly greater at dentin than at enamel margins for all groups. In Group 2, for both adhesive systems, the highest microleakage was observed at dentin margins. Further, dentin-adhesive interfaces were not uniform and gaps were found by SEM and CLSM. Conclusions: The SEM and CLSM images demonstrated high variability of dentin-resin interfaces among saliva-contaminated groups. Rinsing the saliva and re-applying adhesive might be the best way to reduce the effect of saliva contamination on bond strength and microleakage.