Background. Interstitial electrostimulation (IES) is used to treat spinal pain syndromes. The phenomena occurring in tissue around the electrode that is connected to a vertebra remain unknown. Objective. To reveal the mechanisms of action of IES on inflammatory and dystrophic phenomena and blood flow in osseous and paravertebral tissues in low back pain syndrome. Methods. Examinations were made in 64 patients with back pain of vertebral genesis in an exacerbation or incomplete remission with intervertebral disc protrusions. Two homogeneous groups of patients treated with different techniques of electrotherapy were identified. A study group was treated with IES, in which the active electrode as a sterile injection needle was brought into the focus of pathology in contact with the diseased vertebra. A control group received a cutaneous procedure with a 50 Hz current with the same physical parameters. Blood flow in the bone and the adjacent tissues and the intensity of pain syndrome were studied. That in the vertebrae was investigated using needle-rheography and polarography. Results. The intensity of pain depends on circulatory disturbances affecting the vertebral tissues, where a focus of inflammation is formed with signs of free radicals, acidosis, and edema. IES could relieve pain in 90.5% of patients. At the same time, blood circulation in the vertebral tissues considerably improved. Cutaneous electrostimulation was not found to have a substantial effect. The result of the therapeutic effect can be explained by electrochemical phenomena in the plasma from the vessels in the focus of inflammation and by electrophysical processes on the cell membranes of the tissue around its anode introduced. Conclusion. IES is a pathogenetic treatment. In this case, the active anode electrode must be inserted into the focus of pathology, resulting in a contact with the diseased vertebra.