The experiments on animals show the different effects of gold nanoparticles. Gold particles of various sizes may have a variety of toxic effects on the tissues, and more damage is often produced by small nanoparticles. In this work histological and ultrastructural changes of renal parenchyma caused by enteric administration of gold nanoparticles of small sizes (2 nm) were studied used different concentrations of colloidal solutions of gold nanoparticles: 10 µg/ml; 50 μg/ml; 100 µg/ml in drinking water within 7, 14 and 28 days. There were 9 groups of animals (non-linear mice weighing 20-25 g) on different dates of the experiment, as well as 3 control groups of mice, respectively, each term of experiment. Histological and ultrastructural changes were detected in the material of all groups of experimental animals compared with control. In general all small focal alterations relate to a small number of vessels, individual profiles of tubules and single cells. Light microscopy analysis of the overall picture of integrity of renal parenchyma showed that the most pronounced changes are observed in the cortex of the organ. Medulla is less affected. It identifies, first of all, microvascular disorders, then the renal tubular epithelium changes and finally, a minor involvement of interstitial elements in the response. Tubules of nephrons compared with the renal corpuscles undergo more changes at all dose levels of exposure and in all periods under study. Signs of dystrophy and necrobiosis often relate to the cell cytoplasm and less of their nuclei. Evidence of microvessel disorders detected in the renal cortex is not dependent on the dose of administered nanoparticles already in the early stages of the experiment. Histological findings as a whole are confirmed by the presence of ultrastructure alterations, that points to the primacy of cell damage.