BACKGROUND: Several risk factors for ectopic pregnancy (EP) have been identified, but the site of implantation of EP has been little studied. METHODS: A total of 1800 surgically treated EP was registered between January 1992 and December 2001 in the Auvergne EP register and the women concerned were followed up. In this large population-based sample, we studied the distribution of EP sites, immediate complications, determining factors, and subsequent fertility. RESULTS: EP sites were interstitial (2.4%), isthmic (12.0%), ampullary (70.0%), fimbrial (11.1%), ovarian (3.2%) or abdominal (1.3%). No cervical pregnancies were observed. Complications and treatment depended on the site of EP. In multivariate analysis, the only risk factor associated with EP site was current use of an intrauterine device (IUD), which was more frequent in distal EP. The 2 year cumulative rate of subsequent spontaneous intrauterine pregnancy (IUP) increased progressively from interstitial to ovarian EP. Fair concordance (weighted kappa = 0.31) was observed between the sites of two successive EP if they were homolateral. CONCLUSION: In addition to providing an accurate description of the sites of implantation of EP, this study shows that current IUD use 'protects' against interstitial pregnancies, which are the most difficult to manage. It shows that subsequent fertility tends to be higher in women with distal EP.