Background: Background: Prostate Specific Antigen (PSA) is a molecular marker of prostate cancer (PC). I most countries, standard of care suggests annual PSA testing in all men over 50 years of age; and for men at high risk, the test is recommended from 40 years of age. Due to low Specificity and low sensitivity of the PSA test, a large number of unnecessary biopsies occur every year. This low specificity can be due to the fact that PSA is found in both benign and malignant lesions of Prostate tissue. To date measurement of the percentage of free PSA, have resulted an small improvements in specificity of PSA testing. Thus, the development of a simple blood test to detect prostate cancer that exhibits higher specificity compared to PSA could have the potential of reducing biopsies performed due to false positive screening results and improve the quality of medical care. Methods: We have investigated the utility of aspartyl (asparaginyl) β-hydroxylase (AABH) as a prostate cancer biomarker. AABH has been detected by immunohistochemical staining (IHC) in a broad range of cancers including Prostate Adenocarcinoma through out the world. AABH have been detected by IHC in more than 97% of tumor specimens tested (n > 200) while absent in normal and non cancer tissue. We have developed a sandwich ELISA test for the detection of AABH in serum samples. Preliminary results showed an accuracy of 91- 94% for detecting cancer patients from non-cancer patients in different types of Cancer. Here we have utilized this assay to detect AABH levels in the sera of patients diagnosed with Prostate cancer (biopsy proven, pre-treatment samples), compared to non-cancer individuals. Results: AABH was detected above a threshold level of 1.2 ng/mL in 91% of the sera of PC patients (n = 60), in all different stages and grades of Prostate Cancer. All non-cancer individuals (n = 30) had AABH values below the threshold. Further study of direct comparison of AABH to PSA levels (n = 4,000) is underway. Conclusions: Our data suggest that measurement of serum AABH levels may help to detect Prostate Cancer in early stage and potentially reduce the number of prostate biopsies performed due to increased high serum PSA.