The article presents data on the change in the cellular composition of the lymph nodes of the white rats, males of reproductive age, who received intramuscular opioid analgesics - nalbuphine every day for six weeks. The weekly dose of nalbuphine was gradually increased, creating a model of physical opioid dependence according to the patent of Ukraine No. 76564 U. All experimental animals were divided into 8 groups.Morphometric method was used to determine the relative number of cells of the lymphoid series - small, medium and large lymphocytes, blasts and plasmocytes in the cloak zone and the embryonic center of the secondary lymphoid nodes and brain strands of the lymph nodes. Morphometric studies were performed using a system of visual analysis of histological preparations.It was established that nalbuphine in the lymph nodes causes reactive and destructive changes: the number of large lymphocytes increases in all structural components of the lymph node with a maximum after 4 weeks, respectively, the relative number of small lymphocytes decreases in the nucleus centers and brain tracts, the relative number of plasmocytes in the brain strains increases sharply . In all structural components of the lymph nodes hemocapillaries and venules are dilated and full-blooded, around vascular edema and partial damage to the walls of the microvessels.One week after the discontinuation of nalbuphine, the relative number of lymphoid cells in the structural components of the lymph nodes does not return to the indicators of intact animals, no reversible changes are noted.