The effect of prolonged oral administration of gold nanoparticles of various sizes on the structure of the liver, spleen and lymph nodes of mature laboratory rats and their offspring was studied. The morphometric study was performed using the system of digital image analysis of medical Mikrovizor µVizo-103. The detection of conglomerates of gold nanoparticles in tissues was carried out using the dark field microscopy method. It was found that gold nanoparticles of sizes 2 and 50 nm cause the most pronounced morphological changes in the organs, which indicates the size-dependent character of their effects. In the liver of the group with 50 nm gold nanoparticles administration the expressed dystrophy of hepatocytes and activation of monocytic-macrophage system were observed. In the spleen and lymph nodes, the processes of proliferation and differentiation of immunocompetent cells and macrophages were activated. Oral administration of gold nanoparticles during pregnancy in females was accompanied by an increase in the number of hepatocytes with necrobiotic changes and an increase in the number of non-parenchymatous elements in the liver of the offspring, most pronounced in the groups with the administration of 2 and 50 nm gold nanoparticles.