During a survey on the incidence of Aspergillus in clinical environments, we found some interesting isolates that were morphologically similar to Aspergillus parasiticus , but differed in the color of the colonies and in the pattern of their conidial ornamentation. In the present study, those isolates were characterized using a polyphasic approach. A phylogenetic analysis was carried out, based on partial fragments of the acetamidase ( amd S) and O -methyltransferase ( omt S) genes and the internal transcribed spacer (ITS) region of rDNA. This information was combined with a detailed morphological and physiological study that included afl atoxin production and assimilation profi les of different carbon and nitrogen sources. The phenotypic and genotypic results support the proposal of a new species, Aspergillus novoparasiticus , phylogenetically placed in a distinct sister clade to that of A. parasiticus . The former has lobate-reticulate conidia and does not produce aspergillic acid on AFPA or organic acids on CREA, while A. parasiticus has echinulate conidia and produces aspergillic and organic acids. In addition, this new species, as well as A. parasiticus , produces afl atoxins B1, B2, G1 and G2.