['To assess the level of a bone-formation marker, the amino-terminal propeptide of type I procollagen (PINP), for its utility in indicating bone metastasis in patients with prostate cancer.', 'Several bone formation markers, i.e. PINP, the carboxy-terminal propeptide of type I procollagen (PICP), bone-specific alkaline phosphatase (BALP), and bone Gla protein (BGP), a bone resorption marker (pyridinoline cross-linked carboxy-terminal telopeptide, ICTP), and prostate specific antigen (PSA) were measured in 40 patients without and 25 patients with bone metastasis. No patient had undergone previous treatment, except for six who developed bone metastasis while undergoing hormone therapy.', 'All markers except BGP were significantly higher in patients with bone metastasis than in those without. The levels of PINP correlated best with the extent of disease, although the levels of PSA, BALP and ICTP also correlated well. While PINP had the largest area under the receiver-operator characteristic curve, PSA, BALP and ICTP also produced useful curves.'] Is the serum level of the amino-terminal propeptide of type I procollagen a sensitive marker for prostate cancer metastasis to bone?