Background: Prostate Cancer (PC) is the most common form of cancer in men in the United States. In their lifetime, approximately 1 out of every 6 American men will develop PC. The chances of developing PC increase dramatically after age 50 with more than 72% of cases occurring in individuals over 65 years of age. Methods: We have investigated the use of aspartyl (asparaginyl) β-hydroxylase (AABH) as a cancer biomarker. We have developed a sandwich ELISA for its detection. Here this assay was utilized to screen sera from patients with prostate cancer and PSA values in various ranges. Results: AABH levels were assessed in sera from 263 individuals with PC and 73 men over 50 years of age not known to have cancer. The levels of AABH in the two groups were > 3.00 ng/ml and < 3.00 ng/ml, respectively. The overall sensitivity and specificity of the test were 97.5% and 96%. AABH and PSA levels were also compared. The AABH values and sensitivities in individuals with PC and PSA values in the ranges < 2 ng/ml, 2-4 ng/ml and > 4 ng/ml were > 3.00 ng/ml, 99% (n = 115); > 3.00 ng/ml, 98% (n = 64) and > 3.00 ng/ml, 95% (n = 114). Conclusions: The present study of AABH indicates that cancer group can be clearly distinguished from normal healthy controls. Moreover, the study indicates that AABH might be used to identify disease in individuals with questionable PSA values. These results support to the establishment of routine screening of serum AABH as a means to detect those who need referral for prostate biopsy. The use of AABH testing may enhance current prostate cancer screening practices by both identifying individuals with low but suspicious PSA values who should be recommended for biopsy and reducing the number of false biopsies indicated by positive PSA tests. Serum AABH levels are significantly elevated in individuals with prostate cancer. Using a cutoff value of 3ng/ml, overall sensitivity of the assay for prostate cancer is 97%. The test has a specificity of 96% in healthy men over 50 years of age. AABH is elevated in prostate cancer tissue but NOT in normal prostate or in Benign Prostatic Hyperplasia (BPH). Serum AABH levels are NOT correlate with PSA levels.