Purpose: To compare the shear bond strength of four single-bottle adhesive systems (Prime & Bond NT, Single Bond, Gluma Comfort Bond, Gluma Comfort Bond + Desensitizer) bonded to moist and dry dentin. Materials and Methods: A column of resin-based composite was bonded to human dentin using the dentin bonding systems following manufacturers' directions (n= 12). For half the specimens, the dentin was dried completely after acid etching (air dried for 10 s). For the remaining specimens, the dentin was left moist (glistening appearance with no puddles) after acid etching. All specimens were thermocycled for 1,000 cycles at 6-60°C, placed in a fixture on an MTS machine and loaded in shear until failure. Results: Statistical analysis revealed that dentin condition (moist or dry) was significant for Prime & Bond NT, Single Bond, and Gluma Comfort Bond. Bonding to moist dentin produced higher bond strengths than bonding to dry dentin. For Gluma Comfort Bond + Desensitizer, no statistical difference was found between bonding to moist vs. dry dentin. Over all, Single Bond and Gluma Comfort Bond bonded to moist dentin produced significantly higher bond strengths than all other groups.