Physical activity is associated with an increased bone mass and a reduced risk of hip fracture. There are, however, no data from population samples of men and women concerning the effect of regular levels of physical activity on the risk of vertebral deformity. The aim of this study was to determine the relationship between regular physical activity and vertebral deformity in European men and women. A population survey method was used. Thirty-six centers from 19 European countries participated. Each center recruited a population sample of men and women aged 50 years and over. Those who took part received an interviewer-administered questionnaire and lateral thoracolumbar radiographs. Subjects were asked about two dimensions of physical activity: (1) the level of physical activity undertaken either at work or at home on a daily basis at three different age periods: 15-25 years, 25-50 years, and 50+ years; and (2) the amount of time spent walking or cycling out of doors each day. Spinal radiographs were evaluated morphometrically and the presence of vertebral deformity was defined according to the McCloskey method. In total, 14,261 subjects, aged 50-79 years, from 30 centers were studied, of whom 809 (12.0%) men and 884 (11.7%) women had one or more deformities. After adjusting for age, center, smoking, and body mass index, very heavy levels of activity in all three age groups were associated with an increased risk of vertebral deformity in men (odds ratios, age adjusted [OR], 1.5-1.7; with all 95% confidence intervals [CI] excluding unity). No increased risk was observed in women. Current walking or cycling more than 1/2 h/day was associated with a reduced risk of vertebral deformity in women (OR 0.8; 95% CI 0.7-1.0). We conclude that regular walking in middle-aged and elderly women is associated with a reduced risk of vertebral deformity. By contrast, heavy levels of physical activity in early and middle adult life are associated with an increased risk in men. These differences are of relevance in understanding the epidemiology of vertebral deformity and planning programs of prevention.