A 3-year-old boy’s testicles sometimes descending and sometimes not descending may be a symptom related to cryptorchidism, and it cannot be ruled out that it is related to the environmental temperature. 1. Cryptorchidism: it belongs to a kind of congenital developmental abnormality, the typical manifestation is that the testicles can not descend into the scrotum normally, and may stay in the inguinal canal, retroperitoneum, the entrance of the scrotum, etc. Most boys will have their cryptorchid testicles descending automatically after 3 months of birth, and the probability of cryptorchid testicles descending automatically will be reduced with the increase of their age. 2. Environmental temperature: if the boy does not belong to cryptorchidism symptoms, need to consider with the environment, the temperature is low when the testicle retraction, the temperature is high when the testicle drooping, this is the scrotum of the normal physiological phenomenon of thermal expansion and contraction, such a situation do not have to worry too much. Parents are advised to pay more attention to observation, and if necessary, take the boy to regular hospitals for medical checkups to make a clear diagnosis, and if there is any abnormality, timely treatment.