This study will image male subjects with CRPC undergoing second-line anti-androgen therapy (enzalutamide or abiraterone) using 18F-DCFPyL PET/CT for detection of metastases and therapeutic monitoring, with correlation to standard-of-care imaging (CT and bone scan) and clinical follow-up over a 1-year time period. Subjects with CRPC and planned treatment with evidence of metastases on standard-of-care imaging (CT and/or bone scan) will undergo a baseline and mid-therapy 18F-DCFPyL PET/CT.