Common causes of testicular hardness include epididymal cysts, inflammatory calcification of the epididymis, testicular tumors, testicular syringomyelia, and epididymal tuberculosis. The testicles in the scrotum are a pair of smooth and slightly oval organs. The early appearance of a hard lump in the scrotum, which gradually changes from small to large and is not painful, should be taken seriously as it may be a possible occurrence of malignant tumor. Acute epididymitis or orchitis can also cause swelling and hardening of the testicles, but accompanied by redness and swelling of the scrotum, and even fever and other systemic symptoms, which can usually gradually become soft after antibiotic treatment. Hard lumps formed due to inflammatory calcification may still be felt after the symptoms of epididymitis disappear, and general medication is ineffective. When the testicular syringomyelia is large, the affected side of the scrotum is swollen and hard in texture, which can be cured after general surgical treatment. Epididymal tuberculosis often has a previous history of tuberculosis, including urological tuberculosis or pulmonary tuberculosis, and clinically requires differential diagnosis with other diseases. Testicular tumors are mostly painless hard masses, and surgical treatment together with radiotherapy is the treatment for testicular tumors. To sum up, the occurrence of hard lumps in testicles mainly includes the occurrence of epididymitis, testicular tumor, epididymal tuberculosis, syringomyelia and other diseases. Under normal circumstances, it may not be possible to feel the hard lumps unintentionally, which should be found and treated in time.