What if only the left testicle has dropped?

If only one testicle, usually the left, has descended into the scrotum by puberty, it is called cryptorchidism. This condition is fairly common, occurring in about 3% of full-term male infants and 30% of premature male infants. In up to 75% of these infants, the testicle will descend spontaneously into the scrotum during the first year of life, usually within the first 6 months.

Only about 1% of males have an undescended testicle after puberty. An undescended testicle is at increased risk of cancer and should be surgically moved into the scrotum during childhood.