The relevance. Microelementosis (imbalance of certain microelements in the body, ME) is considered as one of the most important clinical and pathogenetic components of degenerative and inflammatory joint diseases. ME can play the role of co-factors involved in the processes of articular inflammation. Objective. To study the levels in the hair and to assess the clinical and pathogenetic significance of osteoassociated ME (cobalt — Co, copper — Cu, iron — Fe, lithium — Li, manganese — Mn, lead — Pb, strontium — Sr, zinc — Zn) at a variety of arthritis — rheumatoid (RA), chlamydia-induced (ReA), psoriatic (PsA), gouty (PA) and osteoarthritis (OA). Material and methods. There were 262 patients under observation, among them 89 persons suffered from RA, 31 — ReA, 35 — PsA, 49 — GA and 58 — OA. The distribution of males and females in these groups was 1 : 2, 2 : 1, 1 : 1, 11 : 1, 1 : 3, respectively, the average age of the patients was 47, 34, 42, 48 and 58 years old, while the duration of clinical manifestations of disease was 10, 4, 11, 7 and 12 years. ME in the hair was examined by atomic absorption spectrometer with electrographite atomizer «SolAAr-Mk2-MOZe». Results. All patients with arthritis are prone to have microelementosis in hair. All nosological forms of joint pathology are associated with a significant decrease of Mn level in hair, when the level of Pb and Fe accumulated. Only RA was characterized by the absence of changes in the hair level of Co, PsA — of Cu, PA — Li and Sr. If, in comparison with healthy persons, the PA proceeds with an increased concentration level of Zn in the hair, the OA is characterized by an increased level of ME, that has a certain differential diagnostic value. There is either direct relationship between the hair and blood serum indexes (Mn, Pb) or multi-directional (Fe) ones. Microelement blood composition depends on the activity level, clinical and laboratory signs of disease, the prevalence of articular process, aggravation of bone destructive changes in the joints (subchondral sclerosis, osteocystosis, osteouzur, epiphyseal osteoporosis, etc), the presence of systemic osteoporosis, spondylopathies (osteochondrosis, spondyloarthrosis) and extra-articular manifestations of arthritis (lesions of skin, muscle, peripheral neural system, lymph nodes, internal organs). Blood indexes of Co, Cu, Li, Mn, Pb, Sn and Zn during RA and PsA may have a certain prognostic value. Conclusions. All nosological forms of arthritis are associated with a significant decrease of Mn level in the hair, when the levels of Fe and Pb accumulate, which are involved in the pathogenetical development of RA, ReA, PsA, GA, OA and determine their clinical course. In the future it will be possible to indroduce more rational medical technology of diagnose and treat joint diseases, to develop medications for correction of microelementosis, improve the prediction of quality of therapeutic interventions effectiveness.