[AIM: Rheumatoid arthritis (RA) is commonly associated with secondary osteoporosis.The BsmI polymorphism of the vitamin D receptor (VDR) gene has been implicated in the pathogenesis of osteoporosis. However, little data is available on the relationship between rheumatoid arthritis and the BsmI polymorphism. In this study, Hungarian frequencies of BsmI polymorphism genotypes were compared with those found in other countries. METHODS: In this study, 64 RA patients and 40 healthy controls were tested for VDR gene BsmI polymorphism genotypes.The frequencies of the B and b alleles were correlated with densitometric and laboratory markers of bone metabolism as well as with laboratory markers of arthritis. RESULTS: Among control subjects, the frequency of the BB genotype (27,5%) was relatively higher than in other European populations. In RA patients with secondary osteopenia/osteoporosis the BB genotype was rarer, while the bb was more common than in control subjects. Markers of bone metabolism showed that the presence of the B allele in RA patients was associated with a lower bone mineral density and an increased bone loss, while the bb genotype was associated with a higher bone mineral content. An increased osteoclast and osteoblast activity was observed in patients with the B allele, as determined by biochemical markers of bone metabolism. Rheumatoid factor titer, an important laboratory marker of disease progression in RA, was significantly higher in bb patients compared to patients carrying the B allele. CONCLUSION: Our data suggest that the imbalance in B and b allele expression may be involved in the pathogenesis of osteoporosis and perhaps of rheumatoid arthritis.]