A GC-MS procedure was carried out for the simultaneous and unequivocal quantitation of both potato phytoalexin (rishitin and lubimin) accumulation and the rate of disappearance of polyunsaturated fatty acids (PUFA) and some of their esters tested as possible elicitors. Potato 5-lipoxygenase and lipolytic acyl hydrolase play a key role in hypersensitive response (HR) induction. As expected, arachidonic acid, its hydrolysable esters, and eicosapentaenoic acid elicited much higher HR than the other PUFA tested, although the latter were equally affected by potato 5-lipoxygenase. Hydroxyl radicals appear to be actively involved in the browning process. The polyaminoacid poly-L-lysine did not show any eliciting activity.