A non-randomized controlled trial was conducted in two family medicine centers. The objectives were to evaluate whether or not a systematic prescription by family physicians of a screening mammography to women aged 50 to 69 belonging in majority to a disadvantaged socio-economic group, would permit to reach at least 60% of them and to explore which factors were associated with compliance to the prescription. The experimental intervention consisted in the prescription by the family physician of a mammogram to those patients found eligible for the screening procedure irrespective of the reason for encounter. A total of 468 of the 870 women who consulted a physician during the study period were eligible for a screening mammography. In the experimental group, the mammography prescription rate was 89% for eligible women. At the end of the study, 58.8% (95% Conf. Int.:51.9%-65.7%) of the women in the experimental group and 13.4% (95% Conf. Int.:9.4%-17.4%) of those in the control group had passed a mammography (p < 0.0001). The adjusted odds ratio for the family physician's intervention was 14.98 (95% Conf. Int.:7.86-28.58). Women over 60 years of age and those who perceived themself more vulnerable to breast cancer were more likely to respond positively to their physician's recommendation. This study confirms that family physicians can effectively reach, in the area of clinical prevention, individuals who might not be reached otherwise.