Aspergillus species found abundantly in the outer environment and hospital setting may lead to serious morbidity and mortality particularly in patients with suppressed immunity This retrospective study was aimed to investigate the antifungal susceptibilities of Aspergillus spp isolated from aspergillosis cases being hospitalized Aspergillus spp. isolated from samples of the patients with suspected fungal infections between January of 2002 and October of 2007, were investigated A total of 678 samples (420 lower respiratory tract, 202 sterile body fluids, and 56 biopsy/tissue specimens) from 569 patients were included in the study. The samples were incubated in 25 degrees C and 35 degrees C on brain-heart-infusion agar supplemented with blood and on Sabouraud dextrose agar Gram and Giemsa stained samples were also examined by microscopy Mold type of fungi were identified by conventional techniques "Invasive aspergillosis" was described according to criteria of Invasive Fungal Infections Cooperative Group of the European Organization for Research and Treatment of Cancer. A.fumigatus (n= 8), A.flavus (n= 2) and A niger (n= 2) were isolated from 12 patients' samples (2.1%), 9 of them were lower respiratory tract and one of each was ascid, brain biopsy and pleural fluid specimens. All of those patients have had an underlying diseases such as malignancy The susceptibility of the isolates to caspofungin, voriconazole, itraconazole and amphotericin B was tested by broth microdilution susceptibility testing and to posaconazole by E-test (AB Biodisk, Sweden). The lowest minimum inhibitory concentration (MIC) (<= 0.125 mu g/ml) values were detected for caspofungin and posaconazole for Aspergillus spp, however, the highest MIC values were detected for amphotericin B (> 1 mu g/ml) MIC values of the all strains except one, were detected as <= 0 5 mu g/ml for voriconazole and itraconazole In one A niger strain itraconazole MIC value was 2 mu g/ml Since the number of other species was low, MIC(50) value was determined only for A fumigatus strains and it was found that the highest MIC(50) value was for amphotericin B (2 mu g/ml) and the lowest MIC(50) values were for posaconazole (0.064 mu g/ml), caspofungin (0 064 mu g/ml), itraconazol (0 25 mu g/ml) and voriconazol (0.25 mu g/ml). Since caspofungin and posaconazole revealed the lowest MIC values, they should be taken into consideration in choice of therapy of aspergillosis cases in our hospital.