Glucocorticoid (GC)-induced osteoporosis mostly affects trabecular bone of vertebrae. Only 30% of vertebral fractures are symptomatic, yet both clinical and radiological vertebral fractures have been associated with increased mortality and morbidity. The aims of this cross-sectional, outpatient-based study were to measure the prevalence of asymptomatic vertebral fractures in a large sample of post-menopausal women given GCs for different diseases; to compare prevalence of asymptomatic vertebral fractures according to disease, GC treatment and major risk factors; and to assess the quality of life in GC users with and without asymptomatic vertebral fractures. 551 patients referring to 39 centers as outpatients for their programmed follow-up and satisfying the inclusion criteria were included in the analysis. Each patient underwent structured medical interview (including dose and duration of GC therapy, major risk factors for osteoporosis, the quality of life questionnaire of the European Foundation for Osteoporosis (QUALEFFO) and a back function score questionnaire), thoraco-lumbar radiographs and subsequent morphometry; for 253 and 437 patients, respectively, lumbar spine bone mineral density (BMD) assessed by dual energy X-ray absorptiometry and calcaneal bone stiffness assessed by quantitative ultrasonometry were available. The prevalence of asymptomatic vertebral fractures resulted >37%, with >14% of patients having two or more asymptomatic vertebral fractures and was much higher than that found in epidemiological studies on healthy women. Distribution of asymptomatic vertebral fractures along the spine showed a bimodal pattern, with two peaks at T7 and T11. The prevalence of asymptomatic vertebral fractures clearly increased with age. Differences in prevalence among diseases were evidenced. When controlled for age, GC cumulative dose, duration of therapy and personal history of fractures, the adjusted prevalences were 30.77% for systemic lupus erythematosus, 33.78% for rheumatoid arthritis, 37.78% for asthma/chronic obstructive pulmonary disease, 43.20% for polymyalgia rheumatica and 43.36% for diseases grouped as "other vasculitides/connective tissue diseases". No significant association was found with GC cumulative dose and duration of therapy. Established risk factors for osteoporosis (except for age, years since menopause and personal history of fractures), lumbar spine BMD, calcaneal stiffness and QUALEFFO score were not associated with number and severity of asymptomatic vertebral fractures. Underlying disease is likely to contribute to the risk of fracture, but disease by itself could not be dissected from GC regimen. Vertebral fractures should be looked for carefully in all post-menopausal women receiving long-term systemic GCs since they can be asymptomatic and are scarcely predictable.