Species of the genus Aspergillus, which often appear as causative agents of opportunistic mycoses (e.g., A. flavus and A. fumigatus), show a high degree of resistance to antifungals. Given that species of the Versicolores series are dominant indoor aspergilli, especially in humid conditions, the question of their role in the occurrence of opportunistic mycoses and their sensitivity to antimycotics arises, about which there is very little information in previous literature. Therefore, the goals of this research were: 1) to create an "in-house" key for the determination of the species belonging to Versicolores series based on the morphology of the colonies in different conditions, which can facilitate the identification process; 2) to test the susceptibility of the isolates present in indoor environment in Croatia to antifungal drugs used in treating systemic mycoses. As a part of the morphological characteristics examination, the colonies were grown for 7 days in the dark and on 6 different media (CYA, CYA20, DG-18, DRBC, MEA and SGA). As a result, a morphological key was developed to identify species from the Versicolores series. All tested types of aspergilli from the Versicolores series tolerate reduced water activity in the substrate well. A minimum of 7 days of colony growth is required for morphological characterization and identification of species from the Versicolores series. The best suited media for differentiation between species and for potential use in phenotypic identification are CYA, CYA20 and DRBC. Antifungal susceptibility test was performed by disc-diffusion method on modified Mueller-Hinton agar with added glucose and methylene blue dye. The obtained results correspond with the existing data on the resistance of species from the genus Aspergillus. Resistance of all species to caspofungin was determined and possible mechanisms of resistance were proposed. Resistance to amphotericin B was present in almost all tested species, which could be regionally present. Intrinsic resistance to fluconazole has been confirmed. Susceptibility to other triazole antifungals varied and a trend of resistance to voriconazole and itraconazole was observed. Posaconazole was the most effective with all tested isolates being susceptible, followed by itraconazole with only 5 resistant isolates out of 20 tested. Least effective was voriconazole with 12 resistant isolates out of 20 subjects.