In a head-to-head trial of teriparatide versus risedronate in 1,360 post-menopausal women with severe osteoporosis (defined as having two moderate or one severe vertebral fractures and a bone mineral density T score of −1 or less), new vertebral fractures occurred in 5.4% of women taking teriparatide compared with 12% of those taking risedronate (P < 0.0001). Incidences of clinical fractures (P = 0.0009) were also reduced in the teriparatide group compared with the risedronate group.