Background: Invasive aspergillosis ia an actual problem of patients with B-cell lymphoma todayAims: To study frequency, etiology, diagnostics and treatment of invasive aspergillosis (IA) in patients with B-cell lymphoma (Hodgkin lymphoma and non-Hodgkin lymphoma), who received cytostatic chemotherapy. Methods: The study included 817 patients with B-cell lymphoma: Hodgkin lymphoma (HL) -363, age from 16 to 65 years (median -33), non-Hodgkin lymphoma (NHL) -450, age from 19 to 74 years (median -50). For the IA diagnosis criteria EORTS/MSG 2008 were used. Results: Frequency of IA in patients with B-cell lymphoma was 4,98% (HL -5,6%; NHL -4,5%, p = 0,49). In patients with NHL, who received anti-relapse therapy, frequency of IA was 10,25%, during induction therapy -2,88% (p = 0,004). The main etiological agents were: A. fumigatus (41%), A. niger (39%), A. flavus (14%). The main risk factors for IA in patients with B-cell lymphoma were: relapse of lymphoma (p = 0,005), B-symptoms and radiation therapy in anamnesis (p = 0,035 and p = 0,041), profound neutropenia (p = 0,000), concurrent lung and renal pathology (p = 0,007 and p = 0,03). The lungs were involved in 100% cases, 4,5% NHL patients had ≥2 organs involvement. Clinical symptoms of IA were nonspecific: fever 68%, cough 48%, dyspnea 32,5%, hemoptysis and pain in the chest were rare -4,7% vs 4% respectively. CT-sings of IA of lungs were also nonspecific: focal changes 63,5%, infiltrates 58,7% and ''ground-glass opacity" 23%; bilateral lung damage -62,7%. Galactomannan test was positive in BAL fluid and serum in 83,6% patients with B-cell lymphoma. The presence of septate mycelium in BAL was observed at microscopy in 15,5% patients. Aspergillus spp. in BAL culture was obtained in 34,7% patients with B-cell lymphoma (HL -20,4%; NHL -46,3%, p = 0,004). ''Probable" IA was diagnosed in 92,9%, ''proven" -in 7,1% of cases. The main antifungal drug was voriconazole -79%. Overall 12-weeks survival in patients with B-cell lymphoma was 84,9% (HL -88,1%; NHL -82,1%). Summary/Conclusion: Frequency of IA in patients with B-cell lymphoma was 4,98% (HL -5,6%; NHL -4,5%), in patients with relapse of NHL -10,25%. The main risk factors for IA were: relapse of lymphoma (p = 0,005), B-symptoms and radiation therapy in anamnesis (p = 0,035 and p = 0,041), profound neutropenia (p = 0,000), concurrent lung and renal pathology (p = 0,007 and p = 0,03). Etiology agents were: A. fumigatus (41%), A. niger (39%), A. flavus (14%). Clinical and CT-signs were nonspecific. The main antifungal drug was voriconazole -79%. Overall 12-weeks survival in patients with B-cell lymphoma was 84,9%.