The purpose of this study was to compare the enamel shear bond strengths achieved with four acid conditioners employed by current enamel/dentin bonding systems (maleic acid, citric acid, nitric acid, oxalic acid) with a 37% phosphoric acid etching technique. The study also compared enamel shear bond strengths between the manufacturers' enamel/dentin conditioner used with an unfilled enamel bonding resin. The facial surfaces of 135 bovine incisors were ground flat and divided into nine test groups of n=15. Conditioning and bonding procedures were carried out following manufacturers' instructions. The phosphoric acid groups were etched for 15 seconds, rinsed for 30 seconds, and dried for 20 seconds with compressed air. All bonding was accomplished at a constant temperature of 21 degrees C and a relative humidity of 60%. A single composite restorative resin (Z-100) was used with all specimens to eliminate variables between composite materials. All specimens were thermocycled 2500 times (5 to 45 degrees C) and had a total storage time of 21 days prior to shear testing on an Instron at a crosshead speed of 1.0 mm/minute. Shear strengths were calculated by dividing load at failure by specimen area. A light microscope was used to determine failure mode. The data were subjected to Bartlett's test for homogeneity of variance and were found not to be homogeneous. The Welch Test was applied and indicated that the treatments used had influence on bond strength at P<0.05. There was no significant difference in bond strength values between traditional phosphoric acid/enamel bonding resin and Mirage Bond Dentin and Enamel Adhesive, Clearfil Liner Bond System, and Scotchbond Multi-Purpose Dental Adhesive System.