The Aspergillus fumigatus group splits into the anamorphic A. fumigatus series and the teleomorphic Neosartorya fischeri series. The species A. fumigatus Fresenius is the most common species within the A. fumigatus series. Forty-seven clinical isolates out of the A. fumigatus group were obtained from patients with diseases such as localized and invasive aspergilloses or allergic disorders due to Aspergillus and were mainly isolated from respiratory secretions. Isolates were studied concerning macro- and micromorphological parameters. All isolates were shown to be isolates of the species A. fumigatus Fresenius. In general, the macro- and micromorphological variability between the different isolates was low. Four isolates (DSM 10661, DSM 10662, DSM 10705, DSM 11069) showed significant differences towards the type strain A. fumigatus Fresenius ATCC 1022; one of these isolates was highly atypical (DSM 10705).