Two common cultivars of sugarcane in Réunion (R570 and R579) were tested for their resistance to the stem borer Chilo sacchariphagus Bojer, a key pest in Southeast Asia, Indian Ocean islands and Mozambique. The laboratory and field trials showed important differences in varietal response to the borer damage only when the larvae started penetrating into the internodes. All the results confirmed the great susceptibility of cultivar R579 on the basis of speed of penetration, survival rates and damage patterns. The delay of penetration observed on R570 led to higher mortality of young larvae and consequently less damage. Resistance mechanisms were also noticed in the stem where larval tunnels were found much narrower than on R579. Different methods and devices were set up and developed to investigate the mechanical resistance of R570. Penetrometry studies indicated that penetration of an R570 internode required 15-50% more energy than that of R579, depending on the penetration site. On this cultivar the internal induration zone was also characterised and this may also account for the difficulty of larvae feeding on these tissues. An overview of results obtained from various methods is presented and further investigations to better understand these resistance mechanisms are discussed. (Autors' abstract)