This in vitro study compared the shear bond strengths of current dentin adhesives. Freshly extracted human molars were prepared to a flat surface and treated with dentin adhesives and composite resin light polymerized in a plastic matrix. Completed samples were stored in 37 degrees C water and thermocycled 1,500 times. Samples were sheared at the tooth/composite resin interface using a wire loop. The reliability index varied significantly between materials. Large coefficients of variation were found for all dentin adhesives. One dentin adhesive was able to achieve a bond strength to dentin that was 47% of the control bond strength of enamel.