Purpose: To investigate the thresholds of restorative intervention in dental caries treatment, based upon the lesion depth seen in radiographs, among Brazilian dentists working in small cities. In addition, the threshold of restorative intervention was compared with demographic and work-related characteristics. Material and Methods: The studied population comprised dentists (n = 89) who were working in 2000 in 20 small cities of the Midwest region of the Southern Brazilian State of Santa Catarina. Four different radiographs were shown of extracted premolars fixed upon a plaster base. The criteria for the radiograph analyses were proposed by Nuttall et al (1993). Results: Of investigated dentists, 16.7% would restore a carious lesion confined to the outer half of the enamel and 33.3% would restore a carious lesion in the outer and inner half of the enamel, but without involving the enamel-dentine junction. The percentage that would restore lesions in the outer half of dentine was 91.7%. Dentists who had attended postgraduate courses in areas of interest of this study tended to adopt a more conservative treatment when compared with dentists who had not attended (p 0.01). Conclusions: There was a great variation in the thresholds of intervention based upon lesion depth seen in radiographic images among the investigated Brazilian dentists. An interventionist attitude was observed, which could result in over-treatment. It is highly recommended to educate general practitioners from the studied region in performing early diagnosis of lesions and non-invasive care in order to treat initial carious lesions with only remineralisation and monitoring. Keywords: caries depth, decision-making, radiograph, restorative decision, treatment threshold