There is evidence that suggests that early treatment with chemotherapy, immunotherapy or hormone therapy leads to a better response in patients with asymptomatic metastatic castrate resistant prostate cancer (CRPC). This study aimed to predict bone scan positivity in patients with CRPC using prostate specific antigen (PSA) levels and kinetic cutoffs. Five hundred and thirty-one bone scans from 312 clinically CRPC patients at two centres were retrospectively reviewed. In univariate analysis, bone scan positivity was associated with younger age, higher pre-scan PSA levels, shorter pre-scan PSA doubling time (PSADT) and more remote year of scan. In multivariate analysis, pre-scan PSA and pre-scan PSADT were associated with bone scan positivity. The authors went on to develop a table estimating a patient’s bone scan positivity by pre-scan PSA level and pre-scan PSADT, with an accuracy (area under the curve) of 77.3%. In patients with a PSADT < three months and PSA levels ≥50ng/ml, estimated bone scan positivity was 67% compared with 6% in patients with PSADT ≥15 months and PSA <5ng/ml. Further work is however necessary in order to determine the PSA level / kinetics which should trigger a bone scan.