Iatrogenesis is common in elderly patients. This phenomenon could be reduced by improving awareness of general practitioners (GPs). We studied GPs' prescribing behavior to elderly patients, to identify GP and patient characteristics related to cautious prescribing behaviors. The observational study sampled 106 GPs who had consecutively recruited, on average, 12 patients over 75 years of age. GPs completed a questionnaire on their practice and a questionnaire for each patient they recruited, describing their usual care of elderly patients, and criteria for prescribing therapy. GPs' behaviors were studied with five scores and a global prescribing behavior (adequate/inadequate). The relationship between patients' risk of iatrogenesis and GPs' behaviors was studied with hierarchical logistic models. A total of 106 GPs recruited 1,318 patients (mean age 80.7 years, 36% males). A wide variety of behaviors was observed among GPs. Only 40% of GPs had specific prevention-oriented visits, while only 19.2% considered that prevention was optimally implemented in their practice. On average, GPs had behaviors considered adequate in about half of encounters. GPs' global behaviors were more likely to be adequate for patients at higher risk (OR=1.47, 95%CI: 1.10-1.95). Likewise, before prescribing to patients at higher risk of iatrogenesis, GPs were more likely to collect data on financial autonomy, on clinical/biological data, and to adopt good prescription practices, while less attention was paid to patients' physical and psychological autonomy. GPs tended to be more cautious when prescribing to patients at higher iatrogenesis risk. However, overall prescribing behaviors were not optimal. Efforts are needed to improve the quality of care in elderly patients.