Bone involvement is one of the most disabling aspects of type I Gaucher disease and its pathophysiology is still not well understood. As an invasive procedure, bone biopsies are not appropriate in a large population study. The development of sensitive bone resorption and formation tests have allowed the authors to study bone metabolism in a noninvasive manner in a group of type 1 Gaucher patients. Ten type I Gaucher adult patients with mild-to-severe bone disease were evaluated. Bone mineral density and markers of bone formation (total alkaline phosphatase and isoenzymes, carboxyterminal propeptide of type I procollagen, osteocalcin) and resorption (carboxyterminal telopeptide of type I collagen, urinary hydroxyproline, free-deoxypyridinoline and calcium) were measured in patients and in a control group, matched for sex and age. In Gaucher patients, carboxyterminal propeptide of type I procollagen (PICP), a bone formation index, was significantly lower compared with normal subjects (mean 101.17 ng/ml vs 140.75 ng/ml, P = 0.038), and analysis of bone resorption indexes showed a significant increase (mean 4.24 ng/ml vs 2.87 ng/ml, P = 0.012) of serum carboxyterminal telopeptide of type I collagen (ICTP). No significant differences were observed in osteocalcin, alkaline phosphatase, and urinary hydroxyproline. Bone mineral density revealed osteopenia in six patients, with a mean Z-score of ?1.04. It was not possible to show a relationship between sex, splenectomy status, age, weight, spleen, and liver volume and bone density, expressed as a Z-score nor a correlation between Z score and severity of skeletal disease. Results have shown a predominance of the resorption phase in the bone metabolism of Gaucher patients. These markers could be useful in monitoring the effect of enzyme replacement therapy on Gaucher disease skeletal involvement.