A nine-year-old Puerto Rican boy with agenesis of the testicles provided an unusual opportunity to explore the role of the testicles in psychosexual development. The recent literature on the psychological role of the testicles is reviewed. This case report demonstrates that the patient experienced the absence of testicles as a phallic defect. He did not appear to have a mental image of the testicles separate from that of the penis. Surgical implant of prosthetic testicles in latency was of great benefit.