If the testicles are not the same size, it is recommended to always go to the hospital for an ultrasound examination, through which the development of both testicles can be measured for abnormalities. If the difference between the two testicles is relatively large, it is definitely the smaller side that has abnormal development. Pay attention to whether the cryptorchid descends late or whether there is atrophy of the testicles due to testicular trauma. If one testicle becomes large, pay attention to whether there is a tumor in the testicle. Through ultrasound examination, all of them can make a valid diagnosis. If there is no obvious lesion in both testicles and the size is different, there is no need to deal with it. If the enlarged testicle is a testicular tumor, radical testicular resection should be performed. If the smaller side is a testicular atrophy, observation and waiting is recommended as the main concern. One side of the testicle is normal and can complete normal sexual intercourse and fertility.