The aim: to conduct analysis of the accumulation and biodistribution of gold nanoparticles in the structural and functional areas of mesenteric lymph nodes of white rats conducted with regard to the size and duration of the oral administration. The methods of dark field microscopy with Leica DM 2500 microscope were used to assess biodistribution of gold nanoparticle. The histochemical reaction of silver amplification with silver lactate by Danscher was used to confirm its identification. Results: It was found that the gold nanoparticles of 1-3 nm were not detected by these methods in any of the areas of the lymph nodes regardless of the duration of administration, gold nanoparticles of sizes 15 and 50 nm were detected in the form of clusters in the cytoplasm of macrophages and lymphocytes mainly in the mantle zone of lymphoid follicles and brain strands. Conclusion: It was established that the gold nanoparticles of sizes 15 and 50 nm were detected in the form of clusters in the cytoplasm of macrophages and lymphocytes