To investigate the in vitro performance of three one-bottle adhesives by measuring their dentin microtensile strength.Extracted human molars had the dentin exposed on the occlusal surface. The teeth were randomly assigned to three dentin adhesives: Group 1 - Prime & Bond 2.1; Group 2 - Prime & Bond NT; and Group 3 - Experimental (unfilled NT). All materials were applied as recommended by the manufacturer. A high-density resin composite (Surefil) was packed on the bonding area in five increments. Specimens (sticks) were obtained using a diamond disc and were stored in distilled water for 24 hrs. The microtensile bond strengths were measured with a universal testing machine.Group 1: 54.3+/-15.6 MPa; Group 2: 62.0+/-17.6 MPa; Group 3: 54.6+/-16.8 MPa. Although no statistically significant difference was found between pairs of means, Prime&Bond NT showed a tendency for higher bond strengths.