Bone turnover, collagen metabolism, and bone mineral status were investigated in 59 patients with cystic fibrosis and in 72 sex- and age-matched control subjects. In all patients and control subjects serum concentrations of osteocalcin (OC), carboxy-terminal propeptide of type I procollagen (PICP), amino-terminal propeptide of type III procollagen(PIIINP), and cross-linked carboxy-terminal telopeptide of type I collagen(ICTP), and urinary values of cross-linkedN-telopeptides of type I collagen (NTX), as well as total body bone mineral content (TBBM) were measured. Higher ICTP (μg/L) and NTX (bone collagen equivalent/urinary creatinine (nmol/mmol) values were found in prepubertal, pubertal, and young adult patients than in control subjects (ICTP: 15.4 ± 2.1 and 13.2± 1.8,p< 0.001; 23.3 ± 5.3 and 20.1 ± 4.1,p< 0.02; 4.8 ± 1.1 and 4.0 ± 1.0,p< 0.05, respectively; NTX: 1047.5 ± 528.6 and 227.8 ± 71.8,p< 0.01; 997.8 ± 391.7 and 376.3 ± 91.0,p< 0.01; 993.2 ± 398.0 and 73.9 ± 28.5,p< 0.01, respectively). Lower OC and PICP levels (μg/L) were showed in pubertal patients in comparison with control subjects (OC: 20.2± 12.3 and 39.0 ± 15.1,p< 0.01; PICP: 305.8± 130.4 and 436.2 ± 110.1,p< 0.02, respectively). Lower OC and higher PIIINP levels (μg/L) were found in young adult patients than in control subjects (OC: 4.4 ± 3.0 and 7.0 ± 3.1,p< 0.05; PIIINP: 4.8 ± 1.1 and 3.1 ± 1.0,p< 0.001, respectively). TBBM (zscore) was reduced in prepubertal, pubertal, and young adult patients (-0.8 ± 0.4, -1.0± 0.4, -1.1 ± 0.5, respectively). Patients with cystic fibrosis have bone demineralization and imbalance between bone formation and degradation.PIIINP,amino-terminal propeptide of type III procollagen;BMI,body mass index;PICP,carboxy-terminal propeptide of type I procollagen;ICTP,cross-linked carboxy-terminal telopeptide of type I collagen;NTX,cross-linkedN-telopeptides of type I collagen;CF,cystic fibrosis;OC,osteocalcin;TBBM,total body bone mineral content;BCE,bone collagen equivalent