Purpose: To investigate the pattern of decision-making by southern Brazilian dentists regarding the use of restorations in the treatment of dental caries. Materials and Methods: A cross-sectional survey involving 840 dentists, randomly selected in three southern Brazilian states, was performed. Telephone interviews were conducted by three previously trained dentists, in which clinical situations with different-depth radiolucencies, based upon bitewing radiographs, were described. Two other situations, including dark fissures and white spots, were also described. The main outcome measures were the tendency in clinical decision-making in comparison with the number of years elapsed since qualification and attendance on postgraduate courses. Results: The overall response rate was 89.4%: 31.5% of dentists would restore cavities in the outer half of the enamel; 54.5% when the cavity reached the inner half of the enamel, but not the enamel-dentine junction (EDJ); 79.0% when cavities reached the EDJ; and 96.9% when cavities reached the outer half of the dentine. Furthermore, 21.8% of dentists would restore dark fissures without signs of demineralization. Dentists qualified for less than 10 years and those who had attended postgraduate courses were less interventionist. Conclusion: It was concluded that dentists have an interventionist attitude in the making of treatment decisions for dental caries and may be over-treating in several situations. Keywords: diagnosis, dental caries, treatment decision, over-treatment