Purpose: The purpose of this study was to test the tensile bond strength of composite resin to enamel surfaces treated with kinetic cavity preparation (KCP) and acid etching, respectively. Materials and Methods: Plane labial surfaces of 280 human maxillary central incisors were treated with either KCP by varying treatment conditions or phosphoric acid gel. Composite samples were bonded to the pretreated surfaces with a bonding resin. After 24 hours specimens were loaded in tension in an Instron testing machine until bond failure. A two-way analysis of variance was used lo determine significant differences. The failure sites were qualitatively evaluated by SEM. Results: The determined tensile bond strengths and observed failure modes demonstrated that acid-etched enamel has a significantly higher bond strength to composite resin than KCP-treated enamel surfaces. Conclusion: KCP prepared enamel has to be acid etched before bonding lo composite resin.