Aim: The aims of this study were to identify patients with systemic mastocytosis (SM) in Croatia and to analyze their clinical characteristics. Patients and methods: Patients with SM treated at eight hospitals in Croatia were retrospectively identified and their clinical characteristics, treatment patterns and outcomes were analyzed. Results: Twenty patients were included, median age was 40.5years (range 24-77), and most were females (n=12) . Patients with indolent SM (ISM, n=11) predominated, followed by aggressive SM (ASM, n=4), smoldering SM (SSM, n=3) and SM with an associated hematological neoplastic disorder (SM-AHND, n=2). Only one patient (with ASM) did not have cutaneous involvement, and a significant proportion of SM patients had dyspepsia, allergic diathesis, bone pains and osteoporosis. Antihistamines were administered in the majority of the patients, whereas ten patients needed cytoreductive treatment (ISM, n=3, SSM n=2, ASM, n=4, SM-AHND, n=1). Most SM patients in need for cytoreduction received interferon alpha-2a (two ISM, one SSM and three ASM), two received steroids (one ISM and one SM-AHND), one received imatinib (SSM) and the last patient was treated with cladribine (ASM). All patients treated first-line with interferons and cladribine achieved partial remission, whereas two patients treated with imatinib and steroid were refractory. None of the patients discontinued interferon due to drug-related side-effects. After a median follow-up of 33 months, three patients died, one with ASM and two with SM-AHND.The median survival of ISM/SSM patients was higher than in ASM/SM-AHND patients in whom it was 105 months (p=0.009). Conclusion: Clinical characteristics and treatment outcomes of SM patients in Croatia are comparable to those from large international centers. The most commonly administered cytoreductive drug in Croatia was interferon alpha-2a which was shown to be safe and effective.