The aim of this study was to determine whether variation in the level of selected hormonal and reproductive variables might explain variation in the occurrence of vertebral deformity across Europe. A population-based cross-sectional survey method was used. A total of 7530 women aged 50-79 years and over were recruited from 30 European centres. Subjects were invited to attend for an interviewer-administered questionnaire and lateral spinal radiographs which were taken according to a standard protocol. After adjusting for age, centre, body mass index and smoking, those in the highest quintile of menarche (age > or = 16 years) had an increased risk of vertebral deformity (odds ratio [OR] = 1.48; 95% confidence interval [CI] 1.16, 1.88). Increased menopausal age (> 52.5 years) was associated with a reduced risk of deformity (OR = 0.78; 95% CI 0.60, 1.00), while use of the oral contraceptive pill was also protective (OR = 0.76; 95% CI 0.58, 0.99). There was a smaller protective effect associated with one or more years use of hormone replacement therapy, though the confidence limits clearly embraced unity. There was no apparent effect of parity or breast-feeding on the risk of deformity. We conclude that oestrogen status is an important determinant of vertebral deformity. Ever use of the oral contraceptive pill was associated with a 25% reduction in risk of deformity though the effect may be a result of the higher-dosage oestrogen pills used in the past. Parity and breast-feeding do not appear to be important and would appear to have little potential for identification of women at high risk of vertebral deformity.