A relation between experimental elevation of testis temperature and poor semen has been known for over sixty years. Poor semen from elevated temperature due to intrinsic abnormality of testis thermoregulation has been a recent concept. A testicular hypothermia device (THD) was created which when worn by "hard core" infertile males with varicocele, failed varicocelectomy, or "subclinical" varicocele resulted in lowering of temperature with improvement in semen in many. Pregnancies have resulted. The device is noninvasive and well tolerated.