Based on a retrospective study of 52 patients with prostatic adenocarcinoma and bone metastases (stage M1b), the authors analysed the following prognostic factors at the time of diagnosis: age, general status, bone pain, haemoglobin, local tumour volume, ureteric repercussions, pre and post-treatment PAP and PSA levels, Gleason score, and metastatic spread on bone scan. This study demonstrated two predominant prognostic factors for the appearance of early or late therapeutic escape: tumour differentiation established by the Gleason score (P = 0.003), stage of the disease, i.e. local tumour volume (p = 0.001) and bone mass invaded on bone scan (p = 0.0002). The other prognostic factors can be deduced from these two parameters. Qualitative analysis of the initial bone scan allowed patients with peripheral bone metastases to be distinguished from those with exclusively axial involvement. The two-year survival was 50% in patients with peripheral metastases versus 93% in patients without peripheral metastases (p < 0.05). Although bone metastasis constitutes a decisive prognostic factor, the detection of peripheral bone metastases appears to be a factor of poor prognosis.