Introduction. Large testicular differences have been linked to abnormal semen characteristics, including total sperm concentration and total motile sperm count in some studies, although this has not been supported by other research. The objective of the study was to analyze the result of scrotal ultrasonography in contrast to the hormonal background in patients with idiopathic severe changes in semen quality. Materials and methods. After excluding the patients in whom a possible cause of infertility was identified, the study group included 106 patients in whom the following parameters were evaluated: testicular volume, Testicular Asymmetry Ratio (TAR), parenchyma echotexture, echogenicity, the presence of testicular calcifications, solid lesions and epididymal cysts, the semen results and hormonal evaluation. Results. From the studied group, 56 patients (52.83%) had TAR<1, meaning low right testicular volume, 32 men (30.18%) with TAR=1-1.2 were considered with normal testicular volume difference, and 18 patients (16.99%) with TAR>1.2 were considered with a significant lower left testicular volume. There was a significant correlation between the volumes of the two testicles (r = 0.586; p < 0.001). Homogeneous testicular echotexture was found in 67% of patients on the right testis (RT) and 76.4% on the left testis (LT). Regarding testicular echogenicity, 69.8% presented a normo-echoic testicular parenchyma on the RT and 75.5% on the LT. A positive correlation between luteinizing hormone (LH) and follicle stimulating hormone (FSH) was observed (r = 0.671; p < 0.001) and negative correlation between LH and FSH and testicular volume. Conclusions. Larger studies are needed to see whether testicular asymmetry is an important factor in idiopathic oligoasthenoteratozoospermia syndrome. TAR could be a valuable instrument in testicular asymmetry assessment. Considering that patients with RT asymmetry have higher testicular volume than patients with pathologic LT asymmetry, we can conclude that that lower RT volume can have a greater impact on overall fertility than lower LT volume.