International audienceOBJECTIVE: To investigate paternal age effect mediated by biological modifications with use of data from assisted reproductive technologies.DESIGN: National IVF registry.SETTING: Fifty nine French IVF centers.PATIENT(S): A total of 1,938 men whose partners were totally sterile, with bilateral tubal obstruction or absence of both tubes (to avoid bias sampling in analysis of paternal age) and treated by conventional IVF.INTERVENTION(S): None.MAIN OUTCOME MEASURE(S): Risk of failure to conceive defined as absence of intrauterine pregnancy.RESULT(S): The odds ratio of failure to conceive for paternal age > or =40 years was 2.00 (95% confidence interval [CI]: 1.10-3.61) when the woman was 35-37 years old, 2.03 (95% CI: 1.12...