BACKGROUND To date, no strategy for improving early diagnosis of melanoma has been evaluated on a population basis in France. OBJECTIVE To evaluate the efficacy of a general practitioner (GP) awareness and training campaign in a pilot French geographical region (Champagne-Ardenne), including 1.34 million inhabitants, 1241 GPs, 56 dermatologists and a population-based melanoma registry. METHODS All GPs received repeated awareness postal mailings in 2008 and 398 (32.1%) attended training sessions organized by 27 dermatologists. The pre- (2005-7) and post-campaign (2009-11) periods were compared for the following: primary endpoint - the world-standardized incidence of very thick melanomas (VTM) (Breslow thickness ≥ 3 mm); secondary endpoints--the mean Breslow thickness; the proportions of VTM and of thin (< 1 mm) melanomas among invasive cases; and the ratio of in situ/all melanoma cases. Similar measures were performed in the control area of Doubs/Belfort territory (655,000 ha), where no similar campaign was carried out. RESULTS The incidence of VTM decreased from 1.07 to 0.71 per 100 000 habitants per year (P = 0.01), the mean Breslow thickness from 1.95 to 1.68 mm (P = 0.06) and the proportion of VTM from 19.2% to 12.8% (P = 0.01). The proportion of thin and in situ melanomas increased from 50.9% to 57.4% (P = 0.05) and from 20.1% to 28.2% (P = 0.001), respectively. No significant variation was observed in Doubs/Belfort territory. CONCLUSIONS These results strongly support the efficacy of such a campaign targeting GPs and provide a rationale for a larger public health campaign in France, including training of GPs by dermatologists and encouraging patients to ask their GP for a systematic skin examination.