Assessment of occlusal fissure systems and restorations of amalgam in 100 extracted teeth were carried out by four examiners. An initial assessment, made with the naked eye, was repeated with binocular magnification (x 3). The data indicated that restorative decision-making behavior was modified when magnification was used, with an increase in the number of restorations planned for replacement and an increase in the number of tooth surfaces planned for restoration. Statistical analysis indicated that one of the examiners was particularly sensitive to the use of magnification and modified his treatment planning behavior considerably. As part of the process of adapting to the use of magnification, clinicians should review their decision-making behavior.