BACKGROUND: The aim of this study was to investigate possible association between 86-bp repeat polymorphism in interleukin-1 receptor antagonist gene (IL1RN) and quantitative ultrasound (QUS) parameters at calcaneus of Korean males, and the interaction with nutritional factor as an environmental factor. METHODS: Several QUS parameters including broadband ultrasound attenuation (BUA) and sound of speed (SOS) were measured using an ultrasound bone densitometer at calcaneus of 206 Korean males (mean age: 50.7 +/- 11.8 year), and this study group was divided into non-vegetarians (N.=141, mean age 50.9 +/- 12.2 year) and vegetarians (N.=65, mean age: 50.1 +/- 10.7 year) depending on their nutritional status. Also, 86-bp repeat polymorphism in IL1RN gene was performed by polymerase chain reaction (PCR) and agarose gel electrophoresis method. RESULTS: There were no significant differences in genotype and allele distribution of this polymorphism between nonvegetarians and vegetarians, respectively. There were also no significant associations in any QUS parameters among each genotype group in both study groups, respectively. But, there were statistically significant differences among normal, osteopenia and osteoporosis groups in allele and genotype distributions of this polymorphism, respectively (P<0.05). CONCLUSIONS: Taken together, our results suggest that the 86-bp repeat polymorphism in IL1RN gene may be one of useful genetic markers for the severity of osteoporosis in Korean males. Nevertheless, this study is yet preliminary, and further studies using larger sample size will be needed.