Background. Mastocytosis is a disease caused by proliferation and accumulation of clonal mast cells in one or more organs. It is often associated with other hematological tumors. Aggressive forms of mastocytosis (AFM) require specific therapy. In non-aggressive forms of mastocytosis (NFM) symptomatic treatment is needed. NFMs prevail, therefore, the disease often goes unrecognized. Aim. To analyze the clinical course and treatment outcomes in different forms of adult mastocytosis. Materials & Methods. The retrospective analysis was based on the records of patients who received in-person and distance consultation within the period from 11/2008 to 11/2020. The analysis of complaints in disease onset and over time was carried out using questionnaires. NFM patients received symptomatic treatment with antihistamines. To all AFM patients chemotherapy was administered. Results. The analysis includes the data of 58 patients: 39 (67.2 %) women and 18 (32.8 %) men. The median age was 40 years (range 18–79 years), the median age on diagnosis was 39 years (range 1–79 years). In all patients skin rashes were reported. The median age of the first skin manifestations was 25 years (range 0.1–70 years). In-person monitoring was conducted in 34 (58.6 %) patients, 24 (41.4 %) patients received distance consultations. Median follow-up was 56.5 months (range 3–564 months). In 8 (13.7 %) patients mastocytosis was diagnosed in childhood with the median of 9 years (range 0–15 years). The diagnosis was morphologically confirmed in 46 (79.3 %) patients. Main complaints included pruritus (67.2 %), edema and erythema response to various irritants (62 %). In 45 (77.5 %) patients NFMs were reported. The regular symptomatic treatment of 78.8 % of NFM patients consisted only of antihistamines (57.9 %), and 2 (4.4 %) patients noted poor disease symptom control. One (2.2 %) patient died of associated chronic myelomonocytic leukemia. None of NFM patients required cytoreductive treatment. AFMs were diagnosed in 13 (22.4 %) patients, 5 (38.4 %) out of them had mast cell leukemia. The indications for starting chemotherapy were cytopenia (n = 3; 23 %), extensive osteolysis (n = 7; 53.8 %), ascitic syndrome with portal hypertension (n = 6; 46,1 %). Overall survival of AFM patients was 84.6 % (n = 11) with median follow-up of 80 months (range 12–131 months). Conclusion. NFM prognosis is favorable. Antihistamines are effective in relieving complaints of most patients. Cytostatic treatment of AFM in some patients provides long-lasting antitumor response.