The possible risk of the development of hypogonadism, infertility, and malignant neoplasm of the testicles in adults dictates the need to develop and implement diagnostic criteria. The identification of such morphological signs as a decrease in the number and diameter of the tubules, the number of germ cells, the development and progression of fibrosis of interstitium may have prognostic significance. The aim of the study is to develop morphological criteria for assessing the severity of testicular hypoplasia in cryptorchidism in children of different age groups. Material and methods. In the study there were identified three groups, taking into account the age of children with cryptorchidism. Group, I included 12 (34.3%) children aged from 1 to 3 years. Group II was presented by 14 (40%) patients aged from 4 to 10 years. Group III included 9 (25.7%) patients aged from 11-14 years. Results and discussion. Morphological changes in the testicle in cryptorchidism children of different age groups vary: in Group I moderate and pronounced structural changes were detected in 53% of cases, in group II - in 50% and in group III - in 72% of cases. Taking into account the morphological criteria of testicular tissue hypoplasia, in our study in cryptorchidism children, hypoplasia of the mild degree was revealed in 17.1% of cases, a moderate degree - in 31.4%, a severe degree - in 31.4% of cases. Conclusion. Morphological criteria for estimating hypoplasia and grading of the severity of hypoplasia of testicular tissue were determined on the basis of a scoring of morphological characters and morphometric indices.