Parkinson's disease (PD) is the most common cause of disability in the elderly. It is currently recognized as a cause of secondary osteoporosis. To evaluate the prevalence of osteoporosis in PD and detect its risk factors, 52 patients with PD (36 men/16 women) and 52 controls paired for age and sex were recruited. Clinical data including demography, disease duration and disease severity were collected. All subjects had bone mineral density (BMD) measured by dual energy X-ray absorptiometry, dorsal and lumbar spine X-ray, and biological exams (osteocalcin, CTX, parathormon). The mean age of the patients was 60.0 +/- 9.25 years [30-77], and the mean disease duration was 4.9 +/- 4.5 years [0.2-17]. Nine patients (17.3%) were osteoporotic and 28 (53.8%) osteopenic. BMD at the lumbar spine and the hip was lower among patients than controls (spine: 1.031 vs. 1.175 g/cm(2); P < 0.001; hip: 0.968 vs. 1.054; P = 0.02). PD patients with low BMD presented a more severe disease and an insufficient sun exposure and calcium intake. There was a positive statistically significant correlation between patients BMD and body mass index and negative correlation with age, severity of PD, and osteocalcin levels. The prevalence of osteoporosis/osteopenia is high in PD patients and seems related to the severity of the disease, an insufficient sun exposure and calcium intake. This osteoporosis constitutes with falls the major risk factors of fracture in PD patients.