Kinlen LJ, Gilham C, Ray R, et al. - In this reanalysis of a large international case‐control study conducted in 1979 to 1982 (2,274 breast cancers, 18209 controls), this study was intended to calculate the independent effects of age at first marriage (AFM), age at first birth (AFB), and the number of sexual partners, adjusted for parity and other risk factors, by unconditional logistic regression. AFM (a surrogate for age at starting prolonged cohabitation) is was found to be strongly correlated with breast cancer risk, suggesting an effect of close contact. The findings revealed that distinguishing the (probably infective) mechanism might lead to effective prevention of breast cancer. It was noted that the independent effect of AFB is smaller and could be due to residual confounding.