Objective: Changes in biochemical markers of bone formation and resorption were followed over the course of 1 year in premenopausal, perimenopausal and early postmenopausal women. Methods: Sixty-four subjects were analyzed, grouped according to their menstrual pattern, menopausal complaints and endocrinological parameters to be premenopausal (n=20), perimenopausal (n=24) or early postmenopausal (n=20). The parameters studied at four visits during the 12-month study period were the urinary pyridinium cross-links pyridinoline (PYD) and deoxypyridinoline (DPD), and N-terminal telopeptide (NTX) as bone resorption markers, as well as osteocalcin (OC) and bone-specific alkaline phosphatase (BAP) in serum, representing bone formation. The longitudinal changes over time as well as intergroup differences were analyzed using generalized estimating equations (GEE) in connection with Wald statistics. Results: Over the course of 1 year BAP levels decreased in the late premenopausal group (P<0.05). The perimenopausal group exhibited significant changes of PYD, DPD and OC (P<0.01), NTX levels were higher than in premenopause. Postmenopausal subjects had elevated NTX values, while PYD and DPD levels remained close to the perimenopausal range. Only for OC a time effect was seen during postmenopause. Conclusions: Changes in bone turnover already begin in late premenopause, when decreased bone formation may precede increased bone resorption. The rise of NTX from late premenopause through early postmenopause indicates diagnostic sensitivity of this parameter to changes in bone metabolism induced by estrogen withdrawal. PYD and DPD do not follow this pattern, but change significantly with time during perimenopause to then remain largely unchanged in early postmenopause.