BACKGROUND Teriparatide (recombinant human parathyroid hormone [1-34]) reduces fracture risk in postmenopausal women with osteoporosis. We assessed the safety and incidence of new vertebral fractures after withdrawal of teriparatide. METHODS This study is a follow-up to the Fracture Prevention Trial (FPT), a randomized, placebo-controlled study of postmenopausal women with osteoporosis treated with teriparatide (20 or 40 microg) once daily for a mean of 18 months. More than 90% of the women remaining at the end of the FPT continued into the follow-up study (n = 1262). Patients and investigators were unblinded to original treatment group assignment. Women were treated according to standard clinical practice, including elective use of osteoporosis drugs. New vertebral fractures were determined by semiquantitative scoring of lateral thoracic lumbar spine radiographs 18 months after the end of the FPT. RESULTS During the follow-up study, the reduction in fracture risk associated with previous treatment with teriparatide, 20 and 40 microg, was 41% (P = .004) and 45% (P = .001), respectively, vs placebo. The absolute reduction from the FPT baseline to the 18-month follow-up visit was 13% for both doses. Osteoporosis drugs were used by 47% of women during follow-up, with greater use in the former placebo group (P = .04); nevertheless, persistent fracture protection of previous teriparatide therapy was evident. Post hoc analysis also suggests that teriparatide treatment substantially reduced the increased risk of subsequent fracture in women who sustained a fracture during the FPT (P = .05). CONCLUSIONS Vertebral fracture risk reduction by teriparatide administration persists for at least 18 months after discontinuation of therapy.