Aims: The objective of this study was to evaluate the biodiversity of Aspergillus section Nigri populations from Argentinean vineyards by morphological, toxigenic and AFLP analysis. Materials and methods: Five hundred and thirty-eight strains were isolated from grapes during 2006/07 and 2007/08 vintages. The morphological identification and toxigenic profile for all strains isolated were performed. Eighty-eight strains were selected for characterization at species level by AFLP markers. Cluster analysis showed a clear separation into four main groups: A. carbonarius, A. tubingensis, A. niger 'aggregate' and Aspergillus 'uniseriate'. A. carbonarius strains constituted a homogeneous group, while a high degree of genetic diversity was found within the A. niger 'aggregate' and 'A. uniseriate' clusters. The A. tubingensis cluster was the most prevalent group and was clearly separated from A. niger 'aggregate'. Ten strains showed 45% homology with A. tubingensis FRR 5720 ex-type strain and were considered as 'atypical' or a closely related species. AFLP results indicate that no genotypical differences can be established between ochratoxigenic and nonochratoxigenic strains. Conclusions: Aspergillus section Nigri populations on grapes were represented mainly by four groups. A. tubingensis species were separated from A. niger 'aggregate' group and some of their strains produced OTA. Significance and Impact of the Study: This study provides new data on molecular characterization of Aspergillus section Nigri populations in Argentina.