In the framework of a bilateral project Italy – Romania (University of Udine and IC), an experiment was established at the University of Udine Experiment Station in order to: i) evaluate the genetic variability of the tested genotypes for Sclerotinia basal stem and head infection; ii) to test two new alternative screening methods against white head rot; iii) to investigate possible relationships among the different tests; iiii) to find resistance-associated fragments by AFLP analysis. The following tests were used: 1) basal stem infection, 2) ascospore head infection, 3) mycelium culture filtrate injection and 4) oxalic acid injection into the back face of the head. The segregation of responses between resistant and susceptible controls displayed the suitability of mycelium and ascospore tests adopted and the independence of the two tolerance mechanisms. Conversely, tests 3 and 4 showed a poor discrimination of the controls and a complete lack of relationships with mycelium and ascospore infections. Sunflower reaction against S. sclerotiorum may not be restricted to resistance to oxalic acid, but may involve other physiological mechanisms. The inbred line 28R (coming from H. argophyllus wild species) was not only most tolerant against both, basal stem and white head rot infections, but also it gave the best performance in oxalate and culture filtrate tests highlight ing a specific resistance to oxalate.