A melanoma is a tumor disease, which can attack besides the skin also other organs, for example eye, gastrointestinal and urogenital tract. Aggressive progression and therapy resistance are characteristic for the melanoma. There is a continuous growth of the incidence of this disease in the world. That is one of the reasons why there is a growth in number of studies conducted on animal models, which are affected by this disease. MeLiM (Melanoma-bearing Libechov Minipigs) is great example of suitable animal model for studying this tumor disease. In these pigs occurs a hereditary melanoma. The peculiarity of this pig strain is, that there is described a complete spontaneous tumor regression usually within three months after birth. Complete spontaneous tumor regression is very rare in humans. However, there were discovered similarities between melanoma occurring in this pig strain and melanoma affecting humans in biochemistry and histopathology. The animal model MeLiM is very suitable for tumor disease research because of these similarities. Reproduction in the animal model MeLiM is not well understood. It can be assumed, in the MeLiM strain sows with hereditary melanoma occurs changes in the functional morphology of the reproductive organs and there are abnormalities in meiotic maturation of oocytes. The aim of this study was to determine if there are changes in the functional morphology of the reproductive organs in the MeLiM strain sows and if there are abnormalities in meiotic maturation of oocytes. We confirmed in our study that the reproductive organs in MeLiM strain sows are smaller than the reproductive organs in common strain of pigs described in the publications. On the ovary of sows were observed ovarian cysts, but there were no abnormalities in meiotic maturation of MeLiM oocytes, even when the number of oocytes was smaller.