Calcium (Ca), magnesium (Mg) and zinc (Zn) levels of fingernails were measured in 135 patients with osteogenesis imperfecta (OI) and compared with the sex- and age-matched healthy controls. Zinc levels in OI nails were significantly higher than that in normal subjects, but in cases and controls Ca and Mg levels were not significantly different. The ratios of Ca/Zn and Mg/Zn in OI nails differed significantly from those in controls, but a similar Ca/Mg ratio was found in nails of both groups. These results suggest that Zn levels in fingernails may reflect abnormal Zn metabolism in OI. To determine Zn metabolism changes in OI, further studies are needed.