A male with one large testicle and one small testicle can be caused by physiological or pathological reasons, if it is physiological reasons, it is not a disease, if it is pathological reasons, it is a disease, such as testicular atrophy, testicular tumors and so on. 1. Physiological reasons: Usually the testicles of both sides of the male are not exactly the same size, one side is slightly larger than the other, and the existence of small differences is also relatively common. 2.Pathologic causes: (1) Testicular atrophy:One side of the testicle is big and the other side is small, it may also be caused by pathological reasons, the small side may have testicular atrophy, such as testicular arteritis and other causes. (2) Testicular Tumor: If there is a testicular tumor, it may also lead to testicular enlargement. Men with different sizes of testicles on both sides are recommended to go to regular hospitals, cooperate with doctors to complete relevant examinations, and actively treat any abnormalities.