Relationships between the rate of bone resorption (measured by urinary N-telopeptide (Ntx) excretion) and a range of skeletal complications have been evaluated in patients with metastatic bone disease. A total of 121 patients had monthly measurements of Ntx during treatment with bisphosphonates. All skeletal-related events, plus hospital admissions for bone pain and death during the period of observation, were recorded. Data were available for 121 patients over the first 3-month period of monitoring (0 -3 months) and 95 patients over the second 3-month period (4 -6 months). N-telopeptide levels were correlated with the number of skeletal-related events and/or death (r ¼ 0.62, Po0.001 for 0 -3 months and r ¼ 0.46, Po0.001 for 4 -6 months, respectively). Patients with baseline Ntx values X100 nmol mmol À1 creatinine (representing clearly accelerated bone resorption) were 19.48 times (95% CI 7.55, 50.22) more likely to experience a skeletal-related event/death during the first 3 months than those with Ntx o100 (Po0.001). In a multivariate logistic regression model, Ntx was highly predictive for events/death. This study is the first to indicate a strong correlation between the rate of bone resorption and the frequency of skeletal complications in metastatic bone disease. N-telopeptide appears useful in the prediction of patients most likely to experience skeletal complications and thus benefit from bisphosphonate treatment.