Cultivated sunflower (Helianthus annuus L.) is susceptible to Sclerotinia sclerotiorum (Lib.) de Bary. H. petiolaris Nutt is a wild sunflower species naturalized in Argentina. The objective of this work was to evaluate the responses of some accessions of H. petiolaris to S. sclerotiorum inoculation in order to detect potential sources of resistance to be used in cultivated sunflower. An experiment was carried out at the UIB’s experiment field. Inoculations were made on leaves and stems. Lesion mean on leaves was 22 mm and 24 mm on stems. The accession GRR-252 showed mean lesions on leaves significantly longer than in GRR-250. However, there were no differences for stem inoculation. Correlation analysis indicated the independence of leaf and stem responses. Results obtained after the first experimental trial suggest the possibility of detecting some H. petiolaris accessions with a higher level of resist ance to S. sclerotiorum than others.