The invention provides methods for isolating RNA from whole urine and urine fractions for the diagnosis of prostate cancer and/or benign prostate hyperplasia. An exemplary method for diagnosing prostate cancer in an individual, said method comprises: (a) determining the amount of RNA encoding one or more diagnostic genes in the soluble urine fraction of a urine sample obtained from said individual; (b) comparing the amount of said RNA to a reference value for said one or more diagnostic genes, wherein said reference value is derived from the amount of RNA encoding said one or more diagnostic genes in one or more individuals that do not have prostate cancer; and (c) diagnosing said individual as having prostate cancer when the amount of said RNA is greater than said reference value.