Unwanted events of systemic steroids (SS) could be predicted by genetic testing for predisposition to the steroid induced osteoporosis. The current study was designed to investigate association between TaqI polymorphism of the vitamin D receptor gene (VDR), bone mineral densi ty (BMD) and rate of vertebral and extravertebral fractures in patients with severe asthma and long term steroid therapy. The study involved 54 patients (15 males, 39 premenopausal females aged up to 50 years). BMD was measured at lumbar spine and proximal femur using dual X ray absorptiopmetry (Hologic QDR 4500A). Frequencies of TT, Tt and tt genotypes, T and t alleles of the VDR gene (TaqI polymor phism) were analyzed by the RFLP method. The patients with the tt genotype had lower BMD and higher frequency of fractures as compared to the careers of TT or Tt genotypes (p < 0.001) independently on age, daily and cumulative steroid doses, and duration of SS treatment. Testing for the VDR gene polymorphism is thought to allow detection patients at greater risk of steroid induced osteoporosis.