PURPOSE: We evaluated the potential diagnostic utility of PET with the cellular proliferation biomarker, 2'-deoxyl-2'-[ 18 F]fluoro-5-methyl-1-beta-D-arabinofuranosyluracil ( 18 F-FMAU), as an adjunct to multiparametric MRI (mpMRI), in localization of sites for image-guided biopsy in men with suspected prostate cancer. PATIENTS AND MATERIALS: Seventeen men with clinically suspected prostate cancer underwent standard mpMRI and investigational PET/CT with 18 F-FMAU. RESULTS: Tissue samples obtained from 22 image-guided biopsies were examined histologically. There were 11 benign, 6 ISUP grade 1, and 5 ISUP grade 2 tumors. The sensitivity for detection of ISUP 1 and ISUP 2 prostate cancer was 16.7% and 100% for mpMRI, and 50% and 60% for 18 F-FMAU PET/CT, respectively. CONCLUSIONS: 18 F-FMAU PET/CT may be a useful adjunct to mpMRI in image-guided prostate biopsy.