We investigated osteoporosis and fractures in Parkinson's disease in stage II to V according to Hoehn and Yahr's disability scale. The bone mineral density (BMD) of the lumbar spine was measured in 82 patients (24 males and 58 females) and in 99 age-matched controls (28 males and 71 females) using dual energy X-ray absorptiometry, and compression fractures of the vertebrae were assessed on X-ray films. BMD decreased with age in females and was lower in females 60 years of age or over than in males at the same age. BMD in the female patients was significantly lower than in the female controls. The female patients in stage III to V had lower BMD than those in stage II. Both male and female patients with a body mass index (BMI) below 21 showed a lower BMD than those with a BMI of 21 or more. Five male (20.8%) and 37 female (63.8%) patients were diagnosed as osteoporosis. In particular 77.8% of the females aged 60 years or older had osteoporosis. Thirty-three patients (7 males and 26 females) had experienced fractures or were found to have vertebral compression fractures on X-ray films. These results suggested that osteoporosis and fractures are common in female patients with Parkinson's disease and that prevention of fractures must be important especially for patients with osteoporosis.