Vertebral deformities are a major complication of osteoporosis. Although their prevalence is known to increase with age, the absence of reference criteria complicates their radiologic diagnosis. We evaluated variations in the prevalence of vertebral deformities according to the diagnostic method used in 291 men and 262 women older than 50 years included in the European Vertebral Osteoporosis Study. Lateral radiographs of the thoracic and lumbar spine were obtained in all subjects using standardized parameters. Six morphometric and quantitative methods were used to detect vertebral deformities. The prevalence of vertebral deformities, the number of vertebral deformities per 100 subjects and the prevalence of deformities for each vertebra varied according to the method used. With most methods, the percentage of subjects with vertebral deformities and the number of vertebral deformities were similar among the men and among the women. In the women, the prevalence and the number of vertebral deformities increased with age; beyond 70 years of age, however, the prevalence remained stable with advancing age, although the number of deformities per patient increased. In men, the prevalence of vertebral deformities remained stable with advancing age, suggesting that osteoporosis was not the only cause of vertebral deformity in this group. In conclusion, the prevalence of vertebral deformities varies according to the diagnostic method used. In men, none of the six methods evaluated in this study adequately differentiates osteoporotic deformities from deformities due to other causes.