Described herein are method, compositions and kits for prognosis of prostate cancer. The methods include determining the ratio of PCA3 and of a prostate-specific marker expression in a urine sample and correlating the value of the PCA3/prostate-specific marker ratio with the aggressiveness and mortality risk of prostate cancer in the subject. The method for prognosing prostate cancer in a sample of a patient includes assessing the amount of a prostate cancer specific PCA3 mRNA and the amount of prostate-specific marker in the sample; determining a ratio value of this amount of prostate cancer specific PCA3 mRNA over the amount of prostate-specific marker; comparing the ratio value to at least one predetermined cut-off value, wherein a ratio value above the predetermined cut-off value is indicative of a higher risk of mortality of prostate cancer as compared to a ratio value below the predetermined cut-off value.