Background: It is increasingly recognised that, in cancer patients, disease progression is dependent on a complex interaction of the tumour and the host inflammatory response and that the systemic inflammatory response, as evidenced by an elevated C-reactive protein (CRP) concentration, may be a useful prognostic factor. Materials and Methods: The prognostic value of CRP compared with prostate-specific antigen (PSA) was examined in 62 patients with metastatic prostate cancer receiving androgen-deprivation therapy. Results: In all, 41 (66%) of patients died, 38 (61%) of their disease. On univariate survival analysis, PSA (p < 0.05) and CRP (p < 0.05) were significant predictors of cancer-specific survival. On multivariate analysis, both PSA (HR 1.96, 95% CI 1.00–3.83, p = 0.049) and CR (HR 1.97, 95% CI 0.99–3.92, p = 0.052) were independent predictors of cancer-specific survival. PSA concentrations were significantly correlated with those of CRP (r_s = 0.46, p < 0.001). Conclusion: The results of the present study suggest that, in patients with metastatic prostate cancer, the presence of an elevated CRP concentration predicts poor outcome, independent of PSA.